AltimeterTwo

Super easy to use, and small enough to fit in BT50 sized (24mm) tubes. We used it in a few different rockets up to 2.0" and ranging from C to F impulse. The rockets we've used the Altimeter 2 with have payload bays and we drilled three 1/16" vent holes in airframe to ensure the unit would work properly.

Much more reliable and accurate than the Estes version, plus a massive amount of data comparatively. Yes, it's more expensive than the "toy" option, but it's worth it if you really want to collect data about your launches. The Estes one is fine if you just want a fun toy to see how high your low-power kits got, but be warned that it doesn't seem to be as accurate overall.One other thing that the instructions cover, but I want to remind you. If you don't vent your rocket with at least two small holes, the pressure inside the model won't match the outside pressure, and you will not get accurate readings. I know some people might not like making holes in their perfect paint jobs, but if you want any altimeter to be accurate, you need to do this. Just find two unobtrusive places and drill small 1/8th inch holes in the body tube.

For the compactness and features this Altimeter Two has is awesome! Plus it provides a lot of other information such as max thrust, avg thrust, coast time, time of ejection after apogee, descent speed, max speed, and total duration. I love it for redundancy if using a dual deploy onboard computer as it displays numbers and one does not have to count beeps. The USB port is only for charging and not for transferring data. Nonetheless, it is a great addition to make rocketry that much more entertaining and scientifically useful.The button seems challenging to press but once one reads the instructions it is clear just press it like you would normally and it will activate. The display needs to be read at the proper angle as it is not that bright. But it keeps the information as long as it has power so you can read it in better lighting conditions.I was able to use it on two other launches and it worked great even when the nose cone came off but the parachute was stuck inside the rocket. It said the rocket descent speed was 57mph! Alas, it was a 6' long Estes Mean Machine so it is now about a 5'6" Mean Machine and the Altimeter two that was wrapped in 1/2" pipe insulation and a rubber band suspended from the nosecone works great!The only issue I had is I could not get it to charge. After reviewing their website support page I found on tip was to use a USB extension cable and after trying it in 6 different USB ports on two computers I was ready to give up. I even had it fail on a trip to ROCstock due to battery drain. Nonetheless, I the cable works and I now have it fully charged and ready to go next time.

Small in size, Large on features!!!! This altimiter gives you 99% of the data you need to know how your engines perform. Tells altitude, time of flight, speed, etc. Easy-to-use, rechargeable, And small enough to use in most rockets!!!!

I'm only giving this four stars because I've only used it once and I can't account for it's life span, but the initial flight was flawless and it came back with all data seemingly accurate. Easy to use, easy to read display. Worth the money for any rocket enthusiast who wants to see how high your rocket actually went, and fun to look at max speed and acceleration data.

Love it

Tells you apogee, delay time, Mach speed, time of flight, etc....these really are incredible items to have for model Rocketry...rsbhunter

This is a fantastic product that lets you see data without having to download each time. You should buy the small leather case as well, to avoid too much exhaust gas entering the unit. Jolly Logic's biggest asset is their customer service. Great communicators, never leave you feeling like you're hanging, will repair their products if you ship them to CA. Great company, looking forward to more business in the future with them. Their Chute Release emulates dual deployment and is second to none. We use it in our BT70 tubes with AeroTech's 24/40 and 24/60. Again, buy the case for the chute release. Keep it up Jolly Logic!