I'm not sure why there is still an SSR2 to be honest. SSR2.5 finishes down pretty nicely most of the time, and will cut through some moderate swirling, and SSR1 can be used as a finishing polish. I guess if you're working on a softer paint than would safely accomodate 2.5, but wanted to do a one step on some light to moderate swirling, 2 may be the way to go. I've never used it so I really don't know for sure.