These couplers and plugs have a smooth, straight-through bore (NO valves) to permit maximum flow. They are commonly used for hot water supply lines for carpet cleaners and for pressure washers. They are made from solid brass, steel, or 303 stainless bar stock and the couplers have stainless springs and balls. Note the below pressure ratings (steel plugs with a brass coupler are the most common) and DO NOT disconnect while under pressure (no valves). The couplers are also available with a special "sleeve lock bearing" that prevents the coupler sleeve from being accidentally disconnected.