Fine for where they were designed to be installed, but will catch water if mounted on the sides of a hull that leans out and opens the door letting water into the hull. Transoms are a difficult install, so you probably won't sell many for that application, imo.
I recently purchased the large, rectangular scuppers for my 1975 Mako. They look good and work well. They are installed close to the water line so some water does come in through them when there is more weight in the stern but that was not unexpected. I'm happy with the purchase and would buy from T-H Marine again. Thank you.