I just got a dg o series slip on pipe. the difference between the two is the o is oval and the r is round. I liked the oval look, so that's what I went with. I honestly couldn't be happier, it adds a very nice deep thump to the idle, and sounds great on the throttle. it's louder, but personally I don't think it's annoying. still tuning my carb, but I think it has more to do with the removal of my snorkel than the pipe, has a flat spot on acceleration, but it did that before the pipe. only thing that threw me when installing was that it literally just slipped on, there's no clamp. but I love the looks and sounds, and I'd totally recommend it.