Features 1、Made of Stainless steel material, durable in use 2、Suit For: High Carbon Steel Drills,and positively locks anywhere along the bit. 3、As Drill Limited ring, clamping device, positioner. 4、Screw type collar will not damage bits. 5、Used for drilling limit, and prevent drilling too deep Specification Features: Made of Stainless steel material, durable in use Suit For: High Carbon Steel Drills,and positively locks anywhere along the bit. As Drill Limited ring, clamping device, positioner. Screw type collar will not damage bits. Used for drilling limit, and prevent drilling too deep Specification: Size (inside diameter) : 3,4,5,6,8,10mm Material: stainless steel Weight: 48 g / 1.7 oz(approx.) Package list: 6 x spacing ring 1 x hex wrench Package List