This is a set of the JR RG712BX receiver and TLS1-ALT altitude sensor, which were used in a motor glider. The altitude sensor comes with instructions. Having an altitude sensor is convenient for gliders as it allows you to know the altitude. For hand launches, I had it set to beep once at 50m, twice at 100m, and three times at 150m. I used to set the motor glider higher, but now it's necessary to be mindful of altitude, and I think it can be used to check and ensure you don't exceed the altitude limit. I will ship it via Letter Pack. Thank you. Type...Radio Control