Features: Upgrade hardened steel material Overdrive and underdrive gears are optional The front and rear differentials each house a worm screw and worm gear setup to get the power to the axles and create higher ground clearance Note: overdrive in front will pull you faster in the front, it allows you to climb better and reduce . How to calculate the ratio? 16T/12T=1.33 16T/13T=1.23 16T/14T=1.14 2/12T: Increase speed 33% 2/13T: Increase speed 23% 2/14T: Increase speed 14% 16T: Do not increase speed Specifications: Colour: Black Material: Steel Overdrive Gears: 2/12T 2/13T 2/14T Stock Gears: 2/16T Suit For: Axial SCX24 all series, Deadbolt JLU C10 Package Contents: 1 x 12T Worm Gear Set 1 x 13T Worm Gear Set 1 x 14T Worm Gear Set 1 x 16T Worm Gear Set Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.