What are the ridges on a Colt 22 rifle called?

I think they're called rail mounts but I'm not sure. I'm looking to buy attachments for my rifle to put them on but I'm not sure if they ridge things come in different sizes and I'd get the wrong one. This is specifically for the Colt SPR 22 rifle. I go to their website and look at the some of their attachments that I know will fit, but I want to look for other attachments on different websites. What should I search for in order to know it will fit on my rifle? Thanks.