Master Mechanic, Heavy Duty Staple Gun, All Steel Construction, Bottom Loading Magazine, Easy Drop In Loading No Plunger To Lose, Compatible With T50 Arrow Staples Sizes: 1/4" TV #137-190, 5/16" TV #137-364, 3/8" TV #137-406, 1/2" TV #139-337 & 9/16" TV #353-562.