Vortex Cantilever 30 mm Ring, Absolute Co-Witness, 1in Offset for StrikeFire CM- is a part of the high quality and dependable Red Dot Sight Accessories from Vortex. All of the features you need for a price you want. Red Dot Sight Accessories from Vortex are well known for their quality and Vortex Cantilever 30 mm Ring, Absolute Co-Witness, 1in Offset for StrikeFire CM- upholds that standard.