PJS’s knurled gripping surface on the outside of both elements for easy adjusting on all 3/8” ID waterline. The inner workings are constructed using stainless steel and corrosion proof Delrin nylon for years of trouble free service. The PJS Pro Flow is designed with an extra long length extended range of operation for a broad range of opening pressures to allow tuners to find that perfect "sweet spot" no matter how low or high you need it to be.