These are direct replacement parts

One 3x10mm machine cap screw w/washer

Installing in model and connecting battery and servos Linking to transmitter

Designed to mount anywhere under the "ties" of any code size of HO track

One driveshaft

Traxxas 3975 Titan 550 Motor 21T 21-T 1/10 E-Maxx Summit Parts These are direct replacement partsTraxxas Titan 550 Motor 21T E Maxx Features: Fan cooled 21 turns 14 volt Bullet connectors Includes: One Titan 550 motor Specs: Length to end of armature: 78mm (3. 07") Diameter of can: 37mm (1. 46") Length of motor leads: 75mm (2. 96") Shaft diameter: . 125" Fits: Traxxas 1 10 E Maxx Traxxas 1 10 E Revo