"But its the correct size to blank a radiator valve off - so saved time because after removing the radiator the valve leaked - put on this blank until I sourced new valves super job sealed immediatly."
"I bought this based on the excellent reviews to block of the hot fill when I took out my old washer. Unfortunately the ball valve had a slight drip and when I fitted this cap the drip continued. Upon investigation I could see the threads ended before the bottom of the cap (not uncommon on machined parts) but the washer was too thin to seal the cap between where the threads end and the mating faces. As a result I had to put in a 3/4" tap washer that was thicker that I had in my plumbing box and now it seals."