The BK expulsion valve is designed for vacuum suspension systems. It creates negative pressure inside the socket. This valve is positioned in a housing that seals securely against the inner surface of the hard socket near the distal end. The valve expels the air under positive pressure when donning a socket. During removal of the prostheses, the socket seal needs to be released via doffing of the suspension sleeve and seal to allow air back into the hard socket. The XP Valve is an auto-expulsion and easy to install package. This is recommended for transtibial amputation and requires normal socket fabrication.