This is a Geissele Automatics Mount known as the Super Precision, model 05-401S.
The Super Precision T1 Series was developed specifically to work with the Aimpoint T1 and similarly mounted red dot optics. These mounts are precision machined from a single piece of 7075-T6 high strength aluminum. Utilizing Geissele's update of the classic nut and bolt method" this mount will attach your red dot to your weapon with 1"400 pounds of clamping force" and features 3 shear lugs for maximum rigidity and return to zero.
Features:
Precision machine from a single piece of 7075-T6 high strength aluminum
