I got the medium Detroit stainless flats....045 -.105 gauge. I replaced them one at a time just so I made sure to get the lengths right. I checked the relief after I put them on and tuned them up and if there's a difference, it's negligible. They shipped first class mail for 4 bucks and got here in two days. I'm loving them!
BTW, I had medium rounds on there before...don't know what kind they are, they were on the bass when I bought it back in October. I kept them for spares, just in case, though.