HPA FCU BLUETOOTH BOARDDescription: Special designed or single valve and double valves HPA engine Free APP Support 5~12. 6V input voltage Compatibility : If FCU is used with other Trigger Board it can suit for jack and Polarstar single valve double valve If FCU is use with our brand Trigger Board it can be suit all the HPA engin POLARSTAR JACK WOLVERINE REDLINE RAVEN INFERNO Functions: Engine Type: This value is very important as it tells the control unit how many solenoids