From Brotato Wiki
Stats
+3 Melee Damage at the end of a wave
+3 Engineering at the end of a wave
-1 Max HP at the end of a wave
+3 Engineering at the end of a wave
-1 Max HP at the end of a wave
Price
100
Unlocked by
Win a run with Engineer
Item
Robot Arm is an in-game item that can be bought from a Shop or can be found in a Crate. Most Items modify the Stats of the player, and some of them provide additional effects.