I can't say enough good things about Airsoft Junkiez and their fast turn around and customer service. Always top notch from these guys and gals. This board is designed to fit V3 gearboxes. Be sure to have somebody who knows what they're doing install this thing. It's actually quite fragile, and the components can come right off the printed board if installed improperly. The operation is great, and I've used it with the F1 installed in my Ares UMP for 3 years or so. Some major modifications are necessary to accommodate the board, but once installed it's operation is what I've come to expect from Polarstar products.