The SIG SAUER Romeo 9T 1x38mm Prismatic Red Dot Sight, Black, SOR91001 Color: Black, Magnification: 1 x, Objective Lens Diameter: 38 mm, Reticle: Dual Color Reticle, Illumination Color: Green, Red, Adjustment Click Value: 0. https://targetammostore.com/product-tag/400-legend-ar15-upper/