US Tactical Systems Steel 30 mm Scope Rings w/1&Prime; Inserts 1.270&Prime; 4140 chrome-molybdenum steel rings with precision Wire-EDM Construction - No "Lapping" required. Square cross-cut bolts. Precision machined to snuggly fit the Picatinny rail cross-cut slots Genuine HOLOKROME Hex Screws fit snuggly to protect your high-end Optic in all conditions 30 mm Scope Rings with enhanced double "lipped" 1 inch inserts Included Designed for the .50 CAL BMG - Built for all Calibers. Best choice in the industry!