Classic Army SR25 / M110 Version 2.5 gearbox with Gate MOSFET , it has a quick change spring system , has a new M110 spring, high torque gears $60.00 Will fit A&K and Classic army 2.5 extended gearboxes I also have a Classic Army high torque DMR motor $15.00 I will do the whole thing for $65.00 Buyer pays shipping