Razor replacement rear wheel assembly for the Razor MX350 Dirt Rocket and MX400 (version 34 and up). MX350/MX400 Rear Wheel Assembly includes 1 rim, inner tube, tire, disc brake, sprocket, axle, axle spacers and nuts.Dirt Rocket versions can be determined by locating your bar code ID on the bottom of the frame or on the battery cover. The 7th and 8th digit in the series will tell you the version of your product: 01=version 1; 02=version 2; 09=version 9, and so on.