Invena 3/4" BSP (22mm) Pipe Thread Extension Female x Male Chrome Brass - 10mm long

These are not cheap at £6 each. If you are using them to extend the connecting stubs of a shower mixer valve, you'll need two - so that's £12. For that money I'd not expect them to have rough edges and have grip marks on the threads as shown in the photos.Do they fit? Yes, they do. But, as is the case with many items of modern rapid Chinese manufacture these days, they need a better standard of finish. Come on guys, spend another 30 seconds and make items "feel" as well as "look" like you care.I'm sticking at 3 stars because they fit and the chrome is ok, but I'd add another star if they didn't feel like they'd just been made in a school metalwork class.

This product does exactly what you need when installing 10 mm wall boards. The extra 10 mm allows re connection of shower valve...but but..the hexagonal sleeve to allow tightening to old shower valve stubs is too big so there is not enough surface left in the 3/4 to allow good seal. Played around a bit and found the thicker 3/4 rubber washer with PTFE on thread and jointing compound did the trick to get good seal...the hexagon is too big so sealing surface is compromised.