This is an optional Traxxas Steel Wide-Face 1.0 Metric Spur Gear, intended for use with the Maxx 1/10 Brushless Monster Truck and the X-Maxx 8S 4WD Brushless Monster Truck. This spur is available in multiple tooth count options, pick one from the pull down menu above.
Note: This list may not be 100% accurate or up to date, and is meant to be used as a guideline for compatibility.