I designed this to be used w/ a quadcopter and have the door actuated by a 9gm servo attached to the quad. Inside you can place any number of items. This one specifically was to hold a couple parachute men :) Attached to the bottom of my quad with hook and loop for easy on/off. On the walkera runner 250 the servo gets attached to Gear or another unused channel. You can use a wire or even a small piece of 3d 1.75mm filament to act as the pin for the hinged door. Mount this set and your servo, adjust the opening for your servo or adjust your servo programming for your desired run/opening. Then fly and Drop Away!!