Vortex's Precision Matched 34mm Rings are CNC machined from certified USA 7075 T6 billet aluminum and have an extreamly tight tolerance of .0005 inches. They features a lightweight, snag free design and use durable grade 8 fasteners. For typical safe insallation, tighted base screw torque to 45-50 in-lbs and cap screw torque to 15-18 in-lbs. Vortex Optics Vortex Precison Matched 34 mm (.92 Inch / 23.4 mm) Rings PMR-34-92