Originally posted by potatocannon4
What's an IVG?
The IVG is the velocity adjuster. (usually brass and goldish color) The IVG is in the lower hole infront of the back block. You adjust the velocity by unscrewing the cocking rod and putting a 3/16 allen wrench in hex hole. Screwing it in raises velocity & unscrewing it lowers velocity. Screwing the IVG in to far can damage the spring and valve. It can also result in the marker not functioning at all.
What kind of IVG should I buy as an upgrade?
There really aren't any performance advantages to a new IVG. The only real reason you should upgrade the IVG is to make setting the velocity much easier. The Rex Dialer Kit is by far the most popular IVG that allows setting the velocity without removing the cocking rod.
-grammar/additions by spyderman
IVG stands for Internal Velosity Govoner.