"I bought this self cutting valve to make a connection for a washing machine but the connecting point under the sink unit was particularly tight. This valve ( not my first choice for this type of connection) came up trumps and saved me a lot of hassle, and my customer some upset."
"When this valve cuts into the pipe it bores a little hole but doesnt always cut right through so in effect, a little flap is created. this can restrict the flow - as i experienced on an outside tap - and I had to replace it for a compression fitting. If this fitting does cut clean through, the little circle of copper does go into to the pipework and could lodge in another fitting along the line thus causing a problem later on for you, so its not just plumbers trying to squeeze you for money but save you a 'possible' problem later on. Overall, its a handy wee fitting."