The Warne Aimpoint T1 modular mount was designed to offer easy height adjustments between absolute and lower 1/3 co-witness in one package to fit all T1/T2 interface red dot optics. 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 0.180″ thick spacer. Height without insert is Absolute Cowitness. Height with insert is Lower 1/3rd Cowitness. Fits the T1-T2 H1-H2 Crossfire Romeo 5 Red Dot and Holosun 403 503 515 530.