The Killer Tools Bumper Perfect Hole Punch Extension Kit, No. ART251EX, is for use with Killer Tools' Bumper Perfect Hole Punch, No. ART251. The extension kit includes dies for four new rear bumper sensor sizes: 27mm, 28.1mm, 29.3mm, and 38.9mm for VW, Subaru, and more. The extension kit gives technicians the capability to punch the correct sized hole with a finished edge.