Atomik RC Traxxas Rustler 1:10 Aluminum Alloy Caster Block Hop Up Upgrade, Grey/Gun Metal Replaces Traxxas Part 3632 Precision CNC Machined for Factory Spec Fitment. Hardened Billet 6061 Aluminum for Lightweight and Durable Performance. Easy Upgrade from the Original Part. Replaces Traxxas Part 3632. Atomik RC Offers a Full Line of Hop Ups for your Traxxas Rustler 1:10 Available in Red, Blue, Grey/Gunmetal.