The DUO is a reaction shape that was extremely welcome to my bag. It's an earlier shape that rolls throughout the entire body of the lane. I drilled mine 2x5 3/4x1 and left the box finish on the ball. It's a strong, even, continuous shape that is not at all violent at the breakpoint, but extremely predictable and reliable. I found that I didn't have much miss room to the left of my target down the lane, but lots of room and recovery to the right. The 2.49 RG gets it started and the .046 differential is what keeps it stable and predictable throughout the lane. Some people have compared it to the Zen but for me it's a little earlier and a little slower down the lane than the original Zen. I have the most success with it playing in or left of the track area and giving it some room to do it's thing. ALSO, 5% of every sale benefits Big Brothers Big Sisters, which is something that everyone can support!