This is a Steel Spur Gear for the PRO-MT 4x4. Pro-Line has a new upgrade part for the Pro-Line PRO-MT 4x4 - Steel Spur Gear! The Steel Spur Gear adds Strength and Durability to a very important part of your truck. The Steel Spur Gear is CNC machined from Hardened Steel and is Black Oxide Coated to avoid rust. The Steel Spur Gear has been narrowed compared to the stock gear to reduce weight and friction for smooth and quiet performance. This is a must-have upgrade if you plan to put insane power through your 4x4!