Ghost Rings are a type of Sights used on various firearms. The rear is a circle and the front is a post. Some details here : amazon.com/LPA-SIGHTS-Shotgun-Sight-Browning/dp/B08BX1JPZP

it is called a ghost ring because the design was originally for long guns, when the large rear aperture was close enough to your eye to fuzz out. That is not the case when you mount that big ring on the back of a pistol.

it is called a ghost ring because the design was originally for long guns, when the large rear aperture was close enough to your eye to fuzz out. That is not the case when you mount that big ring on the back of a pistol.