The Warne Picatinny Modular Red Dot Riser mount was designed to offer easy height adjustments with the included spacer to fit red dot optics that use a picatinny attachment and require a riser for use on an MSR. Since picatinny mounted red dots can vary in height this mount allows the user to select 2 different heights based on their needs. All riser mounts that we offer share a robust mounting base while the top is engineered specially for different red dot styles. All risers include a 0.180″ thick spacer.