McGard “TUNER” security bolt set (4 bolts + 1 wrench). The Tuner series is designed for rims with a small bolt hole. The outer diameter of the nuts/bolts and wrench in this series is smaller than that of standard (SU) or UHS series (SL) bolts/nuts. Thread 12x1.25. Length to the bolt cone 24.0 mm. Chuck diam 20.8 mm. Wrench size 17 mm. Do not use a compressed air wrench to tighten the security nuts! Each package comes with an ID number. You can order a spare chuck using this code!