8 mm collet set. Collet length varies. 46 collets numbered by diameter of grip opening in millimeters. Also included are two 8 mm draw bars of different length, three specialty 8 mm arbor chucks, one 1 mm ER8 collet with matching 8 mm arbor chuck, 2 spare 8 mm collets, and the wooden tray. Collets are used in high precision machining for watches, clocks, and hobbies requiring small components.