Neil Stremmel, the Director of Rules and Equipment for the PBA, has conducted extensive equipment testing during the 2023 PBA season. Testing has primarily focused on the hardness level of urethane equipment.

Based on these findings, the PBA has decided to raise the minimum manufacturing hardness of traditional urethane and urethane-like equipment from 73.0HD to 78.0HD for all tour levels.

Stremmel wrote a detailed breakdown of the decision-making process in the following letter:

Anyone who has been involved in PBA Tour competition or other championship events over the past several years knows of the urethane hardness issues that have had an impact on the industry. In fact, just earlier last year in March of 2022 the PBA banned any traditional urethane balls older than 2 years old. Then in November of 2022, the USBC published its 3rd Hardness Research Report. This led to the PBA committing to a study of their own. The first step of this new study required a new lab to be built – quite the commitment. At the start of 2023, the PBA announced the latest rule, all traditional urethane balls must be made on or after August 1, 2022. This rule ensured that these balls were made recently (less than a year ago) and must meet the new minimum hardness of 73.0HD. This was all due to a new discovery that certain balls (specifically some traditional urethane balls) were measuring softer over time.

The PBA also stated it would continue to conduct tests in 2023 in order to learn the trends of the newly made balls. Do they continue to get softer, at what rate, how low do they get, do all balls get softer and most importantly does the PBA think that it matters for our level of competition?

Why softness matters

The minimum hardness rule was put in place by the American Bowling Congress (ABC) in the early 1970’s. The reason it was implemented was certain balls had been soaked in Methyl Ethyl Ketone (MEK) and/or other softening chemicals. Soaking a ball made it softer and thereby created an obvious amount of additional hook (it was obvious to bowlers at the time). ABC spent time looking at the situation and determined a soaked ball hooked more. During the early days of my time at ABC and USBC, I asked some people about this situation – and again reconnected with key testing personnel over the past couple of years. What ABC ultimately did was look at footprint (the part of the ball that touches the lane) and then correlate it to hardness via the Rex durometer. They saw at a hardness above 72HD, the footprint had negligible/minimal change, but once the hardness dropped between 72-70HD the footprint began to increase. Then, as the hardness dropped below 70HD, the footprint began to measurably increase. Therefore, that is where they drew the line. Additionally, based on the gauge accuracy of the durometer, publicized by Rex as +/-2.0HD, the limit of 72HD makes sense to ensure the readings truly stayed above 70HD. Historically, bowling balls weren’t known to ever get softer with use. This current situation is a newly understood phenomenon. Setting the minimum hardness specification at 72 in the early 1970’s made perfect sense. If anything, modern balls typically get slightly harder as they continued to cure over time. Nevertheless, for a few years now, we have been seeing traditional urethane balls measure softer with use. That is why we need to understand this situation, determine if it matters to the PBA and if so, fix it.


The data from the field and lab testing during the PBA 2023 season are included in Appendix B. However, the view on the data is very simple – there have been multiple urethane bowling balls from more than one manufacturer that have dropped into the 68’s on the Hardness D scale while in use. Therefore, the answer to the above question of “does it matter to the PBA,” is yes and an adjustment to these types of balls must be made. Let me be clear that in all of my tests, these balls all started above 73.0HD out of the box. The data shows that these balls get softer with use. It only takes 10 shots out of the box for the ball to drop 2-3HD points. You can see this in Appendix B under both the Lab Data and specifically in the “Dry Lane Tests” section of the data. In addition, with continued use they can continue to drop to 68.xHD. So, in simple terms, if a ball starts at 73HD and drops to 68HD it has dropped approximately 5 points of hardness.

There is also a lesson to learn from this scenario. Any type of bowling ball that gets softer with use could become an issue with how much it hooks, where it hooks and how it affects the playing environment. Based on this revelation, the PBA will also consider another rule that if a ball, any type of ball, gets more than 3.0HD points softer with use it will not be allowed in PBA National Tour competition. The ball will be removed from play, researched and addressed accordingly. This will be listed as one of the options below.

List of Options

Now that we have determined the affects, what the data shows and that it matters to the PBA, we need to evaluate options for those change(s) along with the pros and cons of each. Not all options can be implemented on their own and may need to be added to another option.

1. Ban all urethane balls completely. This would certainly solve a lot of issues and eliminate some questions still on the table. So, is this a legitimate option? Is this “fair” to all of the PBA National Tour Players? This style of play has developed and evolved to exist with the reactive balls and some players have learned how to utilize it as a portion of their arsenal – or even as a main part of their arsenal. So is it fair to remove this from them at this point? Is this “fair” to all of the manufacturers? Don’t get me wrong, we need to do what is best for our level of competition first, but it is also important to be fair to our partners as well. As part of the decision making process – in the end, since it is known that some of these balls ultimately get below the set minimum hardness specification (through no fault of the bowler) something must be done to eliminate that situation. Therefore, it is the position of the PBA that one of these options be put in place for the 2024 PBA Tour season.

2. Ban any ball that gets softer with use. Any ball that is tested over time and is found to get more than 3.0HD softer is not allowed in any competition. This would require a continual (and new) testing program to evaluate ball hardness over a given time. The current balls that fall into this category get 2.0+HD softer in 10 shots (as noted in Appendix B). At that rate, the testing would not be overly lengthy. Yet, it may be overly laborious since hundreds of new balls are released each year. The other question is, what if it takes more than 10 shots for a ball to drop more than 3.0 points? Some of the traditional urethane balls tested dropped 5 points over hundreds of shots. This may require continual field testing to find if certain balls that are getting more than 3.0HD softer over time.

3. Raise the hardness of traditional urethane to 78.0HD. The data would indicate that a new minimum of 78.0HD would be the appropriate number if you wanted to be reasonably sure that, even after getting softer due to prolonged use, a ball would not go below the actual 73.0 hardness minimum. The difficulty here is what balls need to start above 78.0? Traditional urethane means something to me as a bowler. However, as a chemist, terms like urethane, resin, plastic, polyurethane, polyethylene and polyester all have different meanings. Different than what bowlers think. If a new ball came out I think we would need a clear-cut way to make sure it is, or isn’t, what we consider “Traditional Urethane” or “Urethane-Like.” If this is the option that we end up deciding on, this will have to be laid out and define in greater detail such that the ball manufacturers and probably the whole industry understands. Our hypothesis/assumption with this rule is; 1. If it starts at a minimum of 78.0 it will stay above the minimum of 73 for the life of the ball. And, 2. It will have less impact on the playing environment.

4. Change the hardness of all balls to 78.0HD. This keeps all balls under the same specifications while still allowing traditional urethane balls to get softer over time. Again, is this “fair” to players and manufacturers? Virtually all balls would be eliminated in a short period of time. Ball manufacturers would need to create and test new equipment while players would need the new equipment soon enough to prepare for next season. While this would keep all balls under one specification, it seems far too drastic to implement all at once at this time.

5. Leave the rule as is and test extensively. This is what we have done the past 2 years. The feedback from the players was pretty clear that they did not like this situation, but if we kicked out every ball that tested below 71.0HD and fined the player, they would need to buy into the process. A negative is it would make it seem as if the player was trying to cheat when they don’t really have much control what their ball ultimately tests at once they complete their squad – other than not using it. In addition, the rule that allows the ball to be tested the next day would need to be removed. To me it doesn’t matter what the ball tests at the next day, it matters what it is on the lane while it is being used. I researched the ASTM Standard and the Rex manual and there is nothing in there about allowing a material to recover overnight. I have concluded that in the past both the PBA and the USBC included this rule to give the bowler one last chance to pass the specification because balls didn’t used to get softer with use then recover over time. Therefore, the removal of this rule would be logical and that would lead to a lot of traditional urethane balls failing the 71.0HD minimum (73.0HD minimum spec minus the +/- 2.0HD gauge discrimination). So many would ultimately fail in my opinion that it would essentially eliminate the usage of the ball. Essentially putting us in the same category as option #1 above.

6. Do nothing. Leave the rule as is, allow balls to get softer over time with no testing or repercussions. As discussed above, this option/conclusion does not fit the data for this level of competition. Therefore, for “fairness” as discussed above, the PBA position is that another option to address this situation needs to be implemented.

7. No balls manufactured under the 73HD minimum rule may get softer with use. Through spot-checking in the field at PBA events, any balls, of any style, that are found below 71.0HD (via Field test) will be removed and/or banned. Individual balls will be removed, entire ball lines will be tested and investigated to determine if they are softening over time, with use. Note, if after appropriate testing, research and evaluation, they can fall under the “urethane-like” category, it/they may be moved under that rule. It may include additional tests depending on the specific situation for that ball(s).

8. All balls must be made since 8/1/22. This will ensure all balls are made to current standards and verify all balls have been manufactured above the 73HD minimum rule. This would not solve the urethane situation on its own and would have to be implemented along with one of the other options. Initially, this would most likely be done on the National Tour only. It could follow on the other PBA tours at a later date. This would not be required as part of PBA LBC leagues or tournaments.

9. What should be done for the PBA Regional, PBA50, PBA50 Regional and PBA Youth tours as well as the PBA LBC program? For fairness and consistency across the board, these changes may be needed to cover all tours, immediately or eventually. This would not affect the PBA LBC leagues or tournaments. 


Whether we create a separate specification for urethane-like balls or ban them altogether, we will have to have a way in the future to determine what a urethane ball is. A chemistry definition cannot easily be determined or verified in the lab. After discussing a few options, I believe the best way to describe and test for the category is very slow or no oil absorption rate. If a ball absorbs oil fairly quickly, it would be considered a reactive ball. If it takes much longer, it is considered a urethane-like ball.

We have a current list of traditional urethane balls which would be the initial “Urethane-Like” balls. If any of these are greater than 78.0HD and made since 8/1/22 they would be legal for PBA National Tour competition after 1/1/2024 (all balls on the list made after 8/1/22 are legal for the rest of this 2023 PBA season). For the future, we would test any new ball for oil absorption and anything greater than 45 minutes would be considered “Urethane-Like.” Any ball in the urethane-like category would then need to be a minimum of 78.0HD. New polyester/plastic balls will mostly likely fall into this category as well, but should have no issue being above the 78.0HD minimum. Any new ball with an oil absorption of less than 45 minutes would then fall into the standard category and be allowed to utilize the 73.0HD minimum. New balls in this category will need a unique identifier, like a pin or marking on the ball.


The PBA decision is to raise the minimum manufacturing hardness of traditional urethane and urethane-like equipment to 78.0HD for all tour levels effective 1/6/2024. Data from testing as shown in Appendix B highlights multiple traditional urethane balls for more than one manufacturer testing in the 68’s for hardness. This drop of 5 points would simply be added to the current minimum hardness of 73.0HD to get 78.0HD as the new minimum. The data indicates that 78.0HD would be the appropriate number if you wanted to be reasonably sure that, even after getting softer due to prolonged use, a ball would not go below the actual 73.0 hardness minimum. The category of “Traditional Urethane” and “Urethane-Like” would have a new minimum hardness of 78.0HD. Anything in that current category (list attached in Appendix C) would need to be verified as meeting that minimum hardness before it would be allowed in PBA Tours. I acknowledge that we did not want to create an additional, separate level of specifications. Nevertheless, among all the options, this has been determined to make the most sense and has the most support. Note: The date of 1/6/2024 is being used to allow an in-progress RPI event to conclude by 1/5/2024. Also note: this has no impact on the current urethane balls and their eligibility to be used in all other competitions. 

Additionally, no balls manufactured under the 73.0HD minimum rule (reactive balls) may get significantly softer with use. Through spot-checking in the field at PBA events, any balls, of any style, that are found below 71.0HD (via Field test) will be removed and/or banned. Individual balls will be removed, entire ball lines will be tested and investigated to determine if they are softening over time and/or with use. Note, if after appropriate testing, research and evaluation, they can fall under the “urethane-like” category, it/they may be moved under that rule. Additional tests may be required depending on the specific situation for that ball(s).

Lastly, starting 1/6/2024, we will implement that all balls to be used on the PBA National Tour must be manufactured on or after 8/1/2022. This will ensure that all balls on the National Tour will all be made at a minimum of 73.0HD. This will only be on the PBA National Tour. 

The updated Rules and Specifications that will take effect on 1/6/2024 due to these changes are listed below in Appendix A.

Respectfully presented,

Neil Stremmel
PBA Director of Rules and Equipment

Frequently Asked Questions

Appendices A-C