ITEM NAME:Metal Crown Differential Main Gear Kit 13T 38T for Axle SCX10 90035 90046JCAU Kw.Features: 1. 1 38T Gear. 1 13T Gear. Easy to install and simple to replace your old differential gear. 1 Gear kit. Big gear size: 36x36x24mm/1.41x1.41x0.94in. Small gear size: 14x14x30mm/0.55x0.55x1.18in.