The vortex certs are off of the listed prices on euro...so example the g3 is listed at 2999, the 30% is off of that price. Only restrictions im aware of us they don't let you use it on clearance or sale items
I bought one of Midpack's cert's and can confirm it takes 30% off the G3 at $2999. I also added on the defender flipcaps which it also took 30% off...and they were all ready marked down to $25 making them $17.49 per flipcap!