for Fronts, the R for Rears. The R's are more concave than the F's, a lot of guys put R's all the way around for that more "aggressive stance" sorta look. But it's been awhile since I looked at getting those wheels. I read too many horror stories on them bending and even breaking, however for a street wheel it'll probably be fine unless you have lots of potholes or otherwise in your area. I'm glad I waited it out and found quality wheels with tires for only a little more than new chinese made wheels would have cost.