The Exterior of the vent is fine and well made but the hinged part of the flat was flimsy. The unit had to be tilted to about 80 degrees to make the flap close. I fiddled with the hinge and the flap stayed open at the vertical angle. I didn't want to bother posting it back because I suspected that a replacement might not be any better. I decided to install it at this non vertical angle as it is at the top of the house and no-one will notice. I had to put a spacer under it and put extra mortar in over the bottom open aspect. If you purchase, ask the supplier to check that the flap closes at vertical 90 degree angle.