This is the factory Ruger 10/22 .22LR 10-round rotary magazine.

This is a Ruger BX-1 10/22 .22LR magazine. This genuine Ruger factory magazine features a black polymer casing, a heat treated spring wire, and steel feed lips for reliable feeding. The Ruger BX-1 10 round magazine is compatible with any factory original 10/22 rifle, SR-22 rifle, 22 Charger pistol, .22 LR Ruger American Rimfire rifle, .22 LR Ruger Precision Rimfire rifle, and .22 LR Ruger 77/22 rifle.