The decals quickly identify the players' bats by uniform number while also ensuring anyone with a keen eye knows which team they play for.
It's not clear at the moment exactly who or how many players on the Braves will use the knob decals, other than that Justin Upton's no. 8 was used as the example above.
One can also see where it could be used to prevent another Billy Ripken "F*** Face" incident from showing up on a baseball card.
photo credit: Uni-WatchTags: Atlanta, Atlanta Braves, MLB