Item No NVK-5212 Description This is Novak's Mod 0.5 Aluminum Pinion Gear Set, which includes three gears (17T/18T/19T). These gears fit seamlessly withNovak's Three-80 Micro Pro Brushless Motor, which is included in the Mongoose Brushless Systems (#3050, 3051, 3052). Novak's Three-80 Micro Pro features a rugged, oversized 1/8" output shaft, which is standard on 540-size motors. These hard-to-find, nonstandard gears can be used with any vehicle that utilizes a Mod 0.5 spur gear, such as Associated's, Kyosho's and Team Losi's micro vehicles and Tamiya's TamTech™ line. THREE SETS AVAILABLE: 11T/12T/13T (#5210): works well on small, tight tracks 14T/15T/16T (#5211): performs great on medium-sized tracks 17T/18T/19T (#5212): excels on large tracks There are exceptions when determining the best gears for specific motors and track conditions, but these gear sets allow drivers the ability to experiment with gear ratios in the search to find the optimal setup.