HS = Holosun; 1st digit = 4 for 2 moa dot only reticle, 5 for 2 moa dot with a 65 moa circle reticle; 2nd digit = 0 for standard accessories, 1 for upgraded accessories (kill-flash filter, Quick release mount and flip lens covers), 3rd digit = 0, 1 or 2 for an infinity 30 mm tube red dot, 3 for a micro red dot Final letter = C for solar, all others for battery powered only.