The T257 is a high-quality vacuum valve. After the valve is laminated in the prosthesis socket, and the stump is placed in it along with a silicone or gel liner, the valve releases air from the socket as the limb pushes it out and does not allow it to return, thereby creating a vacuum and holding the prosthesis on the stump. They velve provides negative pressure in the socket, venting air outside through the vent. It can be used for a vacuum socket system as an alternative to the classic pin-lock technique. These components do not transfer loads. Narrow valve. Used with single lamination. The T257 valve uses a T257A1 plastic laminating mockup.