The series 67 and 68 valves have a robust one-piece stem design with a free of play spline disc-stem connection. The valves have a replaceable seat which covers the full body as a liner and isolates flowing media from the valve body and stem. The replaceable rubber valve seat is vulcanized on a phenolic or aluminium back-up ring. This construction makes this valve very well suitable for both high velocity flow and vacuum applications. The series 68 lug type is not suitable for dead-end services. For this application we recommend using the Econ® butterfly valve series 64 or 68.