"Great little product. As mentioned it has three flaps not two as pictured. It fitted perfectly as a direct replacement for the open vent that was there previously. The centres of the screw holes are about 103mm apart. Top tip: mount it with the extractor fan running. Makes it much easier to get the flaps open! It is made of average quality plastic as the previous reviewer said but I can't imagine why it would need to be any stronger and for £2 what do you expect. Will definitely use these again."
"This flap is like 99% of others in as much as the mounting holes are far too near the hole that the flap covers. I drilled the hole for the duct this one was going to cover with the right size diamond core drill through good brickwork, but as usual when I tried to drill the holes for the mounting screws the edge of the hole in the brickwork broke away. All it needs is a larger mounting flange on the flap so the mounting holes can be further from the hole that it covers. I would be prepared to pay more for the extra material used in a bigger flange."