Centurion upper mechanism with 3/8" diameter oleo struts. Axles installed at angle specified by manufacture and comes with a complete small air system included See part number 3400 for air system description. Bullet proof inner struts installed after 11-15-04. For realistic retraction and extension gear speed, look at our Deluxe 4 Way Valve. Order 1410E when ordering the gear and save $$$$.