Designed to match up with STD 1-piece or STD 2-piece bases, the Leupold STD 30 mm Medium Mounting Ring System fits most rifle models. The rear ring is secured by windage adjustment screws, and both rings are made from forged and machined steel. 0.77"H. Leupold STD 30 mm Medium Mounting Ring System Black - Scope Rngs And Rifle Accessories at Academy Sports