These valves are designed to provide minimum turbulence & resistance to flow when in fully open position.  Sufficiently long guide ribs in the body along with accurately machined wedge guide slots ensure accurate control & alignment of wedge while operating wedges are generally solid type & are accurately machined, precisely aligned & perfectly lapped with renewable seats in carbon steel & integral seats in stainless steel.  All the valves have back seat arrangement as an additional sealing under full working pressure which facilitates replacement of packing with valve under fully open condition.