Hold an extra two rounds right where you need them in a pinch with the SAP Two Rounder. .308 Holder fits case bodies 0.450" to 0.550" in diameter .223 Holder fits case bodies 0.340" to 0.440" in diameter Magnum Holder fits case bodies 0.550" to 0.800" in diameter such as 6.5 SAUM, .338 Lapua and up to .50 BMG This two-round-holder attaches with Velcro to the side of nearly any rifle near the ejection port. Important! You must clean the stock with a good quality rubbing alcohol (91% preferred) and LET THAT DRY COMPLETELY to prepare the surface for proper adhesion of the supplied industrial strength Velcro piece!