Ian we had some on the Corniche, not very good to hang anything bigger than a LILO, buy some proper ones.Roger Whittall has his boat moored behind mine, will have a word if you like.
Disagree with negative comments below - all depends on what you want to hang on the back and what height your bathing platform is relative to dinghy. Have had them for 8 seasons and have found them fine for what I want which is to keep a smallish inflatable (Bombard A300) securely stowed, accessible and easy to deploy on the stern of a sportscruiser.
Of course, if you want to keep an outboard on the dinghy, that's another story.....
Good luck with finding a supplier. Be careful to get all the relationships right (snaps/platform/dinghy at floating height) if you DIY. If you have a bigger boat, a professional will be able to mount the snaps on stainless "L" extensions to drop them to a reasonable height which I have seen and which seems to work.
All this is alright but they look terrible crapish. and who wants to look at the ass end of a dinghy. Proper davits look much better. All in my HOP of course.