Hot Racing XMX38X06 Aluminum Motor Mount TRAOptional Machined Adjustable Motor Mount for the Traxxas X Maxx YOU WILL RECEIVE: Two piece Adjustable Motor Mount with replaceable lock nut Lock nuts are to secure fasteners or shaft with threads A lock nut comes with a nylon insert that conforms to the threads of the screw The nylon insert grip against the threads that reduces the chances of loosening due to the vibration For best performance use new lock nut.