Mansfield 225-5907 Stop Cap for 210 and 211 Flush Valves Mansfield 225-5907-100 Stop Cap for 210 and 211 Flush Valves This is the part that screws on top of flush valve and keeps the flush tower from rising too high When it is broken the flush valve can get hung on it preventing the tower from falling back down to Many times when this part is broken it happens because the toilet is hard to flush and replacing the flush valve seal will make it easier