The McAlpine STW3-R 19mm Water Seal Shower Trap with Universal Outlet is a plumbing component used to connect the waste pipe from a shower to the drainage system. The STW3-R trap is designed to be installed below the shower tray and is commonly used in residential and commercial plumbing installations. The STW3-R shower trap features a 19mm water seal, which helps to prevent foul odours and gases from escaping from the drainage system and entering the living space. The water seal also helps to prevent blockages by trapping debris and preventing it from entering the drainage system.