We scrapped the Staywell, in favour of another brand, which is much sturdier, and easier to fit: needing a round hole (Which is a bit of a bugger if you've already got a square Staywell hole). Mine's fitted in a plate glass door, which cost a fortune at the glaziers. I'll post the brand tomorrow.

Sturdy it may be, but it gave way quickly to our rescue boxer dog, but it's not designed for head-butting!