In recent years, the NCAA has started testing the barrel compression of Fastpitch bats prior to games and tournaments, making sure the bats are compliant with the rules.
Barrel compression is the force to compress the bat barrel a certain distance. If the force to deflect the barrel is less than the leagues' specified force limit, the league notes that the bat may no longer comply with the performance regulations and should be removed from play.
The barrel compression limits were initiated when the composite bat designs and barrel compressions were very similar. There are many ways to design bats to comply with association regulations and recently some solutions have lower barrel compression values than other bats. This does not mean that they are hotter than bats with the higher compression, as all bats must still meet the performance regulation, regardless of their barrel compression, period. All bats must comply with the overall performance limit.