The Spirax Sarco 1810080 is a replacement disc for the BTD52L Steam Trap. This OEM replacement disc is the only wearable piece of the BTD52L trap besides the seat rings which can be replaced with standard o-rings. If your BTD52L Disc is worn to the point were slight lapping is not enough to improve the performance this replacement unit is required. Replacing this BTD52L Disc is easily accomplished without disturbing the piping connections, just ensure complete isolation of the trap from both the supply and return line via flow isolating valves installed upstream and downstream of the unit service is being performed on.