These screw on fins are amazing,. They are very easy to attach and allow the bottle to go much higher and straighter. They are definitely worth the price.

I bought a simple water bottle rocket science kit a while back for my son and we had a blast playing with it until we successfully "landed" the rocket on the roof of his school. I ordered these StratoFins to replace the fins that came in the original kit and am very pleased. Adding these fins to a 2-liter bottle rocket really makes the whole thing fly much straighter. You can still get some wind drift on the way up, but there's no tumbling at all on the ascent. The fins also add some drag to slow down the fall and the whole thing crashes harmlessly onto the ground. One really cool feature of these is that they replicate the 2-liter bottle's cap screw. This makes the design compatible with cable-tie launcher bases, which is awesome. The original fins we got in our kit did not do this so we were stuck using the kit's included rubber stopper as the launch mechanism. Another nice thing about these is that the fins themselves separate from the screw-on collar for storage and travel.

The only minor change I would like to have seen is a more rounded lip along the edge of the fins for a more aerodynamic profile (not that I think the current design impacts performance much). Overall we're thrilled with these and look forward to using them more as we blast our rockets off to even greater heights.

Fins break off. Can be fixed with thick bead of silicone. I had two of the 3 I bought break on the first few launches. I still use them after above repair. If I bought more, I would just put a thick bead of silicone on them before thy broke. Put it on and run finger along like it was caulk. Then another bead after it dries. Haven't had one break since I did that.

Must have item for water bottle rockets! Make sure you have plenty of room. 60psi and it shoots 2 litre bottles crazy high!

StratoFins greatly increase the altitude and stability of a 2 liter bottle rocket. Flies two-three times as high as the plain bottle did. So high, in fact, the wind above the soccer field caught it and blew the rocket into some trees--alas, we never found it. I immediately ordered a replacement set. We are using with the Aquapod Bottle Launcher and the fins work just fine (launcher latch engages raised ring on the fins). You do need to rotate the rocket/fins so they clear the launcher structure.