Hot Racing Hardened Center gear set for use on the TRA 1/16 E-Revo, 1/16 Slash 4X4, 1/16 Summit, 1/16, 1/16 F0RD Fiesta, 1/16 Mustang, and 1/16 Rally. - CNC machined and hardened steel construction - Nitride coated to increase wear resistance, improve fatigue life, and enhance corrosion resistance - Hardened steel construction.