Modified Piercer Body, High Flow for the SMK 501. This does away with the tube, gauze, filter and steel washer if fitted, although they have copied my design. Do not try to fit the Tube, Filter, washer or gauze into our valve piercer body, we have made ours for more efficiency and power. Helps to bring the gun nearer the UK limit of 12 ft. lbs. Standard they are normally between 10 or a little more. The 501 gun can exceed the legal UK limit so keep an eye on the power after any work you do. Bedding in and temperature can affect the power so check regularly. The standard hammer spring can be shortened to reduce the power if required.