Bushings for 709 Metal Stud Punch Holes 7/8" (22.2 mm) Diameter Hole. Bag of 1000. Triple lock design holds bushing securely. Locks securely into metal studs from 24 gauge to 12 gauge (0.6 mm to 2.5 mm). Helps protect wire insulation from sharp edges of metal studs. Makes pulling smooth and easy by preventing hang-ups of cable on raw metal edges.