"The "blind" 15mm end is designed to be used with an olive as a compression fitting in something like a radiator valve. If you want to join the 15mm end to a 15mm pipe you should use a different fitting. This is a cheaper way to use the less expensive 15mm radiator valves so that you can reduce the pipe work to 10mm."
"Why should I have to use a straight fitting to use this reducer? The 15mm end is 15mm outside diameter, which means having to use a straight connector to complete the joint, which of course adds to the cost."
"this reducer can not be used as reducing 15 mm pipe to 10mm because there is 15 mm outside diameter so the same as the pipe, have to be use 15mm coupler so incrase the cost and there is nothink about it in the item description"