I'm using a Becue Prime II 12.0 shaft and I don't have any reason to try another shaft, it has a super long taper, I haven't measured it but it is visibly noticeable and different than any other shaft I've seen, I have used a 12.4, 11.8 as well and to me the difference is so small in size it's not worth talking about, 1/2 of 1 mm, I didn't really see a big difference in performance due to shaft size, I think it has more to do with the taper than the outside diameter of the shaft, what I love about Becue is they aren't trying to improve on shafts they built in the past but are building shafts that have different types of hit, the Engage is a firm CF hit, the Prime II is the most wood like hit of any CF shaft I've tried and the original Prime shaft has the most flex of any CF shaft on the market, not everyone will like the same type of hit, I have also owned a Defy CF shaft and played with wood shafts for years, the Prime II 12.0 shaft is my favorite shaft of all time.