Ipired by NASA JPL ma rove Kaiser walking excavator Lockheed Martin M.U.L.E. / Retarius UGCV Rover was named Challenger because is designed to overcome obstacles BOM screws M2 couteunk head Body 50 mm Servos 10 mm Cove 6 mm M2 lock nuts Suplie: screws gbt-fastener SG90 servo N20 geared DC motor