I have two Norwegian Forest cats who weigh about 13 pounds. They love to look out my windows, but ever since I had new windows put in the windowsills are smaller than they used to be. This left very few windows for my cats to perch on, so I went looking for something I could easily put up and take down that was sturdy enough for my big girls.
This perch is covered in carpet, and it's 13" x 9". It's very simple: there's the rectangular platform and a small arm that comes down from the platform and tightens up against the window trim to provide a brace to support the platform. Installation is a breeze if you have double-hung windows. There are two metal brackets that form a 90-degree angle on the back of the perch, and you simply lift the lower window and slide the metal brackets behind the seal and close the window back on them. Then all you have to do is adjust the support brace: it slides in a track so you can adjust it for many different window sizes, and it also rotates so you can tighten it/get it as close to the wall as possible.
The kit I got did come with the screws necessary to mount it to a wall, but most windows don't need them. The insert says that the window perch will hold up to 30 pounds without the screws, or up to 35 pounds with the screws. My cats are about 13 pounds each, and the perch has worked great for them: I've had it for over a year.
I haven't seen my cats scratching on it, so the carpet still looks new. The only maintenance I have to do is to remove the cat hair that builds up on the perch, and a simple flat, bristled vacuum cleaner attachment does the trick in less than a minute. When it's time to open the window or move the perch to a different location, I can open the window and simply lift up on the bottom and the perch comes up effortlessly with one hand.
The only problem I have with it is that it's not really big enough for both of my cats to stretch out on. I think it would work well for most average-sized cats, but because my two cats are both large-breed cats they are too big to both get on it at the same time.
If you're looking to get a similar perch from Foster and Smith, I got mine during a sale and paid a lot less than the current list price of $37.99. I was glad I didn't pay full price, because the pictures make it look like it's bigger than it really is. I think they use kittens when they take pictures! However, most cat products are a bit small for my cats (think Maine Coon size), so don't let that deter you from trying it out.