It is the spped of bb, while its leaving the innerbarrel of replica. This speed is measured in FPS (Feet Per Second).

1 FPS = 0,3 ^m/_s

1 J = 99 ^m/_s

1 J = 326,7 FPS

Indications v2, v3, v6 does not mean the level of advance, but only shape of gearbox skeleton which was used and selected by the manufacturer depending on the capabilities of the body of the replica. For example, a models of the M4/M16 family, MP5, have a v2 gearbox, while the AK family have gearbox v3.

This is a value that includes the weight of the replica, magazine and other accessories that are include in set without a battery, charger, cleaning rod, etc., etc.

Hop-Up system is used for overclocking bb during the shot (putting it in rotation), through which, it extends its flight path. Acting laws of physics make that bb lift up, while the gravitational force take it down. Appropriate adjustment of Hop-Up, will compensate for these two factors, which result in long and straight flight for longer distance and be greater focus shot (to improve accuracy).