The 13N21 standard Copper Collet 1/25 (0.040) from Weldmark® by CK Worldwide® is a copper, split style collet, compatible with both water and gas cooling methods. A collet is a mechanical clamping device, like a sleeve, that uses pressure and friction to hold an electrode in position within the welding torch. Collets are sized according to the diameter of the electrode used. In this case, it has a 1/25 (0.040) electrode diameter. (Includes 5 per bag)