an inline reg is a secondary regulator which helps to keep an accurate flow of gas in to the marker. For example, youve got an angel air with an output pressure of 500psi, if there was no inline reg on the angel then that 500psi would run straight into the gun. The inline reg takes the 500psi and lowers the input pressure down to 200ish psi. Obviously this applys differently for different markers, the cocker for example has an operating pressure of about 90psi so your inline reg would have to make sure that no more than 90psi was entering the gun.
If i remember right, mags have their own reg at the back of the gun so you dont really need an inline reg, if your running co2 your better off with a co2 expansion chamber because you need to make sure all that nasty liquid co2 has been turned into gas before it enters the gun.
hope this helps, Matski
