This device is a mixer for "Flying Wings" or "V-Tail Airplanes". 

With such a device, both Elevator and Aileron/Rudder functions can be combined together. 

Full instruction leaflet included

Specification
1. Size: 31mm(L) * 8mm(w) * 8mm(H)
2. Weight: 4g
3. Mixing Rate: 1:1 (Fixed)
4. Precision: 200 steps

Brand New sealed packaging - see image 3