Specification: 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm M3: Inner diameter: about 3.2mm, Outer diameter: about 9.8mm, Thickness: about 3.5mm, Height: about 8mm M4: Inner diameter: about 4.2mm, Outer diameter: about 9.8mm, Thickness: about 3mm, Height: about 8mm M5: Inner diameter: about 5.2mm, Outer diameter: about 11.8mm, Thickness: about 3.4mm, Height: about 8mm M6: Inner diameter: about 6.2mm, Outer diameter: about 11.8mm, Thickness: about 3mm, Height: about 8mm M8: Inner diameter: about 8.3 mm, Outer Diameter: about 16 mm, Thickness: about 3.9 mm, Height: about 8 mm M10: Inner Diameter: about 10.3 mm, Outer Diameter: about 18 mm, Thickness: about 3.8 mm, Height: about 8 mm Stop Collar: 3, 4, 5, 6, 8, 10, 12, 16 (mm) The drill stop collar is mainly used for fixed limit drilling depth on the drill bit. Works with standard and brad-point bits, the setscrew type collar will not damage the bits. Carbon steel stops for long-lasting performance. Material: Carbon steel. Hex Shank