Hpi 87137 Roto Start 2 System (Starter Unit) fits Savage X 4.6 Trains With The SR515 a top located With The SR515 a top located button makes binding more convenient than ever while two bind sequence options make the process simpler by allowing you to bind while powering up or after receiver power is connected each with its own dimmer control _ Lights require 16 20VAC and draw a maximum current of 30mA each Lighting adjustment instructions of bottom of package 2V rechargeable "Stick" battery pack and charger Engine back plate is not included Genuine HPI quality spare part to provide easy maintenance and repairs for the HPI Roto Start 2 System