This will provide you with the difference between BBCOR, BESR and ABI. It also provides you with the current BBCOR standards, rules and regulations along with It will also let you know legal and what isn’t.

Below is the breakdown of the current changes in bat performance standards. First, we have some definitions of terms. Second, there is a league-by-league timeline. Third, some of the common questions about the changes are answered.

Definitions

BESR (Ball Exit Speed Ratio)
This was the longstanding test used to ensure that non-wood bats play similar to wood bats. It tests a bat’s “exit speed,” i.e. how fast the ball bounces off a composite or aluminum bat barrel. It has been phased out, because it failed to account for how bats would perform after they have been broken in (Composite bats typically improve with use).

BBCOR (Batted Ball Coefficient of Restitution)
This is the new, more-accurate test that is replacing BESR. Like BESR, it is used to ensure that aluminum and composite bats play similar to wood bats, but it also accounts for how bats perform after they’ve been broken in. That’s because it includes the ABI, described below.
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