Combo-hex clamps are the clamps professional mechanics choose most often. For hard-to-reach areas. Safety-collared, deep-slot screw design helps prevent screwdrivers from slipping. Can be installed with a screwdriver, nutdriver or socket wrench. Screw: 3/8" safety-collared hex-head. Plated carbon steel. Band and housing: 9/16" design, 201/301 stainless steel. Worm type drive. Pipe size inches is plastic pipe sizes. UPC coded.