Climax Metal, H1C-Series: 1-Piece Recessed Screw CollarRecessed screw head provides an outside surface free of major projections for safety. Design fully engages the shaft without marring. Greater axial holding power than set screw collars. Effective on hard and soft shafts. Bore Sizes from 1/8 to 4" in Stainless Steel, Aluminum and Black Oxide Steel.