Midwest Industries. Go with their extended rails. They are amazingly solid and actually MIL-SPEC in that they will come even with the rail on a MIL-SPEC A3. Not Surefire tho. They are good rails but they are quite a bit lower than the reciever rail. Midwest Industries has great service and great products. Their free floating rails rock. They are rock solid. I put one of their rail systems beneath each tire of a Ford Excursion and it didn't bend or get dinged. They have low prices and amazing products. GO MIDWEST! yay!
anyway thats my 2 cents.
EDIT: also their rail system allows the attachment of rails every 45 degrees with some nifty little thingies. They are also rock solid. Midwest Doesn't cut corners to save on production costs but they still retain phenominally low prices.