This part is a parachute release system for SKY HERO multirotor frame. you need part 1, 2 and 3 to get complete system.
You will also needs (not included)
1* HS-81 or HS-82MG HITEC servo
1* HITEC horn bag
6* M3x30 screws
6* M3 nuts
Warning : to get full system, you need to buy the three parts :