i use the turbo-nocks and love them. Beats refletching arrows ill say that upfront. Im not sure where more devasting kills came in to play??? Also i have noticed that there was some eratic arrow flight. I also realized my bow wasnt turned PROPERLY to shoot the nocks so i retuned my bow to shoot them properly. For all you speed demons out there yes they do cause you to pick up a little speed but not a whole lot. I do recommend them but tuning the bow is neccessary like with any other item you add to your bow any time. As far as the wingy thing on the back, well when the bow is tuned properly you should have very little unstable flight. Also looks like to me the arrow would spin faster with no fletching with the turbo on??Some people like fletching some poeple like the nocks. Id recommend trying the nocks, if u dont like them use your flectched arrows. Me personally i went and bought a 1/2 dozen arrows and shot them with the nocks and after a week went by, i had a dozen and half arrows with turbo's on them. Remeber there are negative and positive's to everything. I asked my local shop about them and they said well they were just a trend which is where the statement made earlier comes in to play about revenue they make from feltching arrows (1.50 a piece) helps them produce money. Will you have mroe devasting kills? NO. Will you pick up significant times on the chrono??? Maybe a couple of feet per second. But when the bow is tuned properly I noticed after I started using them my groups were tighter, arrows flew more true than conventinal fletching. Just my experiences.