24 HOLES BUR BLOCKS – Aluminum, Autoclavable – 12 FG Holes, designed for any instruments with FG Shanks (Friction Grip: 19mm) and FGOS (FG Surgical: 25mm) for High Speed Headpieces; 6 FGSS Holes, designed for any instruments with FG Short Shank (Friction Grip & Short Shank: 16mm); 6 RA Holes, designed for any instruments with RA Shanks (Right-Angle Latch: 22mm) and RAOS (RA Surgical: 27mm) for Low Speed Headpieces. Dimension: 55mm x 25mm x28mm.