ITEM NAME:7pcs Countersink Drill Bit Set Adjustable Depth Stop Collar Woodworking Drilling Description Specification: Brand new Material: carbon steel Surface: black finish Diameter: 3, 4, 5, 6, 8, 10, 12mm Color: as picture shows Mainly for fixing the drill bit, limited the depth of drill holes, make depth of the hole consistent More convenient to roundwood mortise Of Use Package included: 7pcs x stop collars 1pc x hex wrench Note: Please allow 1-5mm errors due to manual measurement Item color displayed in photos may be showing slightly different on your computer monitor since monitors are not calibrated same.7pcs x stop collars. More convenient to roundwood mortise Of Use. Mainly for fixing the drill bit, limited the depth of drill holes, make depth of the hole consistent. Surface: black finish. Color: as picture shows.