Glass钢管, also known as Reinforced Plastic Mat (RPM) pipes, are primarily made with glass fiber and its products as reinforcing materials, unsaturated polyester resin, epoxy resin, and other high molecular weight components as basic materials, and quartz sand, calcium carbonate, and other inorganic non-metallic granular materials as fillers. The pipe lengths are available in 6m and 12m, and the manufacturing methods include fixed-length winding, centrifugal casting, and continuous winding processes. The pipes are categorized based on the production method, pressure class PN, and stiffness class SN.