Zero Set is the same as Zero Stop, They just call it something different to separate it from the Zero Stop on the NXS, they call it Zero Hold on the ATACR. Different turret set ups on the three.
These are some fantastic optics, if you don't mind the 30+oz weight, you would have to look hard to find a better optic for the $$
Contact Keefer at Eruoptics, he'll take care of you.
"I ain't here for a long time, I'm here for a good time"
King George Strait