Hot Racing aluminum Differential Carrier (case) for the front or rear differential on the Traxxas E-Maxx, E-Revo, and XO-1. Replaces Traxxas 3978 differential Carrier. Features: - CNC Machined aluminum - Anodized Blue - fits either the front or rear differential you will receive: - one (1) differential Carrier - four (4) ring gear screws requirements: - reused Traxxas spider and output gears (Traxxas 3978), gaskets and O-rings (front Traxxas 3978), and ring/Pinion - thread locking adhesive to keep screws from loosening due to vibration - do not over tighten - use only silicone diff lube comments: - Replaces Traxxas 3978 differential Carrier