I have tried them on the stock APS hop-up unit (see photo below). The 10mm ID x 14mm OD x 2mm W o-ring seems to fit pretty good. That was an easy ...

Finding replacement rails that would fit just right is not so easy. Most of the rails on the market has screw spacing that are just two rail spaces apart. But ...

In this regard, the metal gearbox is more durable than the plastic gearbox; because it can handle stronger spring, longer. And, in turn, it provides you with a ...

Disassembling the gearbox, I found that the trigger post had broken off. Examining the trigger mechanism, I realized that the trigger post is molded as part of ...

The photo above shows the MP5 collapsible shoulder stock. The only thing holding it onto the receiver is a pin. The pin is held in place by the flat-screw next ...

With the AEG, there is a gearbox, where a strong spring is pulled to fire the BB's. Most of the upgrade occurs either within the gearbox or around it. That ...

Photo below shows an APS gearbox with a quick change spring guide (changeable with a 7mm hex wrench). If so, remove the spring guide and the spring first.

Gearbox is locked. This article provides a quick and simple method to reset ... The big flat screw in the middle is to adjust the motor tension to the gearbox.

The gearbox internal has steel gears, metal trigger, plastic piston, plastic piston head. The air nozzle is air sealed version with an internal o-ring.