Do you wish to take your indoor cat(s) outside? I did. I know how they love looking out the windows, especially when the window is open and they can breathe the outside air through the screen.
I've had cats before that we used to let outdoors, but ended up determining that it was better for them to be indoors in a safer environment. So I made the venture to purchase a pet stroller. It looks similar to this one, but it didn't have a cup holder, which is actually a nice addition.
I also chose this style, because it has the upper and rear screen which allows the pet to look up and/or back at me. I think that helps to reassure them that you are nearby, and I can more easily see them.
It worked well for the both of our cats when they were smaller. For now I take them on individual rides. If I were to get another pet stroller at some time, I think I'd go for for a bigger option.
An Amazon reviewer has said that she has used this style for her two cats, who weighed 13.5 and 11 pounds at the time. This stroller's measurements are: height to handle 42"; Interior dimensions 30"L x 13"W x 22"H. So it is more long than wide. It also has a paw rest inside, and multiple screened viewing options.
If your cat hasn't been on a stroller ride yet, then I recommend that you allow them time to get accustomed to the smells of it, and getting in and out of it while stile indoors. If you have room inside, take them for little rides inside your home so that they are more familiar with it before their first outdoor day in it.
If you'd like to check out different styles, you can view more pet strollers for cats at Amazon.