This is the standard piston / cylinder assembly that fits both Mamod and MSS locomotives. It is supplied by our man who sells us brand new high quality Mamod and other manufacturers items. This piston / cylinder assembly is designed to fit both MSS and Mamod locomotives. It carries our normal no-quibble guarantee so you can buy with complete confidence. If you are in doubt about anything in connection with this item or the model it is intended for, why not email us with your question before you make your purchase. We will be very happy to help you - and we always respond quickly!