SR25s are particularly known as DMRs. This is because unlike most other guns, the SR25 has an extended AEG cylinder which gives it a higher volume allowing for more range. This extended gearbox is called the version 2.5. It is partially compatible with version 2 parts. The differences between v2 and v2.5 is the piston, gears, cylinder, and tappet plate. All of which are extended to allow for the higher cylinder volume. A&K and G&G are the primary manufacturers of the SR25. Ares also makes the SR25, however, they use a standard v2 gearbox which disables the additional range that should be available to the platform.