https://www.hackfabhobbies.com/products/12mm-hex-w...

These 12mm Hex Adaptors allow you to attach 12mm hex drive wheels to 1/4" drive shafts. Simply insert a 1/4" shaft (D-shafting is recommended) into the adapter and tighten the set-screws.

Hex is 6mm deep. Overall length of the entire hub is just over 26mm. 1/4" bore for common D-shafting used in pullers and our Evolution pulling sled. Includes m4 set screws and m4x10 button head screws to secure the wheel to the hub (running a washer would be optionally recommended depending on wheel).

Includes:
2x 12mm hex hub w/ set screws and wheel screw