SPEED Airsoft sends in information about the dual purpose use of their SPEED HPA Triggers as they can work with MOSFETs as well... "The SPEED HPA triggers will take full advantage of the M4 HPA engine in an AEG, by reducing the trigger pull tension and giving it full adjustability externally.

In addition to the M4 HPA engine conversion, the SPEED HPA triggers will also work with any M4 AEG with a MOSFET conversion that has an on-board micro-switch.  The SPEED HPA trigger gives the MOSFET conversion the exact tuning ability equal to the HPA system.   A MOSFET conversion with the SPEED HPA trigger is essentially equivalent to a HPA conversion on the field, but without an air hose connection.

For more info, visit SPEED Airsoft at www.SpeedAirsoft.com or get your SPEED products from SPEED authorized airsoft dealers worldwide."