This is the 8PC DRILL BIT SHAFT DEPTH STOP COLLARS RING SET 3-16MM WOODWORKING WOOD DRILLS.

Product Features:

8-PC Drill Bit Depth Stop Collar.
Drill Bit Depth Stop Collar 
 
Drill Limited ring，  clamping device， positioner .
Works with both standard and brad-point bits.
Setscrew type collar will not damage bits.
Positively locks anywhere along the bit.
 
Hardened and Tampered
High Carbon Steel Drills
sizes:3mm 4mm 5mm 6mm 8mm 10mm 12mm 16mm
 
package included:
8 x Drill Bit Depth Stop Collar(notice :without drill bit)
1 x wrench