The Holosun Spacer raises 510C optics to a lower 1/3rd co-witness; Compatible with HS510C wide-view open reflex Green/Red Dot Dight; Made of high-quality 6061 T6 Aluminum with an anodized Surface Finish; Long-lasting construction remains durable and strong from shot to shot; This Holosun Black HS510C Riser increases the dot height to 1.63in; The Spacer mounts between the 510C Gun Sight and the QD mount; Mounting hardware is included in the 510C Spacer delivery package; Perfect hunting and shooting sight accessory for your shotgun; Dimensions: 1.6in x 0.98in x 0.95in