The series is called sorrority strip-off.
I had the whole collection at some point but I think I moved it to DVD's.
This is my favorite of the whole thing because of the the two girls that appear around the 3 minute mark.
Jenny and Christine. Jenny was notable for always being "genuinely shy" every time they asked her to get naked but then letting them their fingers up her asshole or something. Christine, by contrast, really was shy and didn't like showing her pussy. This was one of the most explicit scenes they ever released of her: