Novak's additional four 5mm Mod 1 Steel Pinion Gears 17T-23T (#5111-#5117) feature a high-strength hardened steel construction and are precision machined. These gears are compatible with Novak’s Ballistic 8 Brushless Motors (#3801, 3802), Ballistic 550 (#3504-3507), and other motors with a 5mm output shaft. Each gear includes a set screw.