These are the only small units available for scale tail-wheel retraction. They f... These are the only small units available for scale tail-wheel retraction. They feature spring centering and a steering mechanism. The unit operates from a conventional retract servo or air cylinder and has self-locking down. Note: You will need to purchase a standard Air Cylinder (F-RB165) with these retracts.Recommended for model weights up to 12lb (5443g).