Seamless one-piece vessel Waterco's Micron Fiberglass Filters are made from continuous strands of high quality fiberglass filament, wound under controlled tension to create a seamless, impervious vessel. This process produces a filter that is free from welds and seams. No special tank linings are required to fight corrosion. Waterco's revolutionary winding technology further strengthens the vessel, which can be built to withstand a working pressure up to 150psi.