Swagelok sample cylinders are made of 304L and 316L stainless steel to resist corrosion and DOT rated to 1,800 or 5,000 psig (TPED cylinders rated to 1,450, 1,885, or 4,350 psig), which allows sampling at gas wellheads as well as on-site refineries. Each cylinder is hydrostatically tested to at least 5/3 the working pressure.