Little League International changed the approved bat list for 2018 (Effective January 1, 2017). Please click the link to get more information. All bats used during a game MUST have the USA stamp (as seen below).  Umpires will be required to check all bats prior to each game as well.

http://www.littleleague.org/learn/equipment/baseballbatinfo/USA-Baseball-Bat-Standard-FAQs.htm