The Black Gold Ambush single pin scope is on a vertical dovetail so you can zero it out at the top range of the "Dial-of-Death" on the fixed bracket or the dovetail bracket that goes along with a Ascent Ambush sight. This way you'll be able to instantly put your sight to a default distance of choice without looking or when in the dark. A single pin is preferred by many archer's to eliminate the "clutter" of multiple pins in the sight housing. Sight housing is 1 3/4".