Holosun Technologies AEMS CORE X2, Red Reticle, 2 MOA Dot, Fits 1913 Picatinny Rail, Lower 1/3 Co-Witness Mount, Black AEMS-CORE-X2-RD AEMS CORE X2 improves the AEMS platform by increasing accuracy with an advanced optical system that cuts parallax by 50%. It also introduces a new four-post, lower 1/3 co-witness mount. AEMS CORE X2 remains backward compatible with the original AEMS mounts.