bma_addon-1.12-4.0.5.1.jar is a beta file of the Minecraft mod Class Armor : Berserker, Mage and Archer, made for Minecraft 1.12. It was published on October 6, 2017 and is 0.3 MB in size. Pre-release builds can contain bugs — back up your world before installing. For the full description, screenshots and every other version, visit the Class Armor : Berserker, Mage and Archer mod page.
How to install: Put the .jar into the mods folder (.minecraft/mods) and start Minecraft with the matching mod loader profile.