This is the optional Tamiya RC 06 Hard Coated 25T Pinion Gear. Aluminum construction, hard coated for durability Compatible with 06 module spur gears used in a variety of RC vehicles Rounded teeth design, for greater resistance to wear and lower drivetrain friction loss 25T Pinion Gear with 3mm Set Screw jxs 11/03/14 ir/jxs &