This is the Traxxas Telemetry RPM/Speed Sensor Wire Retainer. The wire retainer installs inside of the sensor-ready gear cover (sold separately) to properly position the RPM sensor and wire (sensor sold separately). Note: This item number includes two parts: the wire retainer for Slash, Bandit, Rustler, Stampede 2WD and Ford raptor models, and the wire retainer for the E-Maxx.