MI-MRO-1/3 --- (Midwest Industries Trijicon MRO Red Dot Optic Mount Lower 1/3) 1.7oz. MI-MRO-CO --- (Midwest Industries Trijicon MRO Red Dot Optic Mount Absolute Co-Witness) 1.4oz. Compatible with Trijicon MRO red and green dots Lightweight, super strong, and snag free design Designed to withstand real world use by military or law enforcement agencies. Billet machined from Aerospace 6061 T6 aluminum. Milspec hard coat anodized finish. Steel cross bolts that engage stainless heli-coils for superior clamping force. All installation tools and hardware are included. 100 percent made in the USA with a MI lifeti Mfg: Midwest Industries, Inc.