This is a Ruger BX-25 X2 10/22 50rd. Magazine. Ruger came up with an innovative design to couple two magazines together. It comes with a rubber dust cover to prevent the intrusion of dirt and debris for the on deck magazine. Once the first 25rds. are used, all you have to do is remove the dust cover and flip the mag. over. As reliable as the standard BX-1 10-round Ruger rotary magazine. Stainless steel feed lips are designed to present cartridges into the action at a 30 degree angle for better feed reliability. Stainless steel, constant force spring provides feed consistency round after round. Anti-tilt follower is injection molded from a high lubricity polyacetal for consistent reliability. BX-25 X2 magazines will work with any factory original Ruger 10/22 Rifle, SR-22 Rifle, 22 Charger Pistol and 77/22 Rifle. The BX-25 will run reliably with a wide variety of ammunition. However, you may experience malfunctions (“jams”) when using subsonic ammunition or ammunition with heavy coatings of bullet lube. In some instances, cleaning the magazine may improve reliability, but in other cases you may need to switch to a different type or brand of ammunition to get the full use and enjoyment from your BX-25 X2 magazine. Please also be aware that some .22 LR magazine loaders are prone to damaging cartridges. If you experience stoppages while using magazines that were loaded using a magazine loader, please try loading the magazines by hand and determine if reliability improves. The BX-25 X2 magazine requires no lubrication. If it becomes necessary to clean the magazine, loosen the screws on the right and left side of the magazine with a 3/32’’ hex tool. Next, separate the two halves, lifting the right side from the left side, and then lift out the spring, throat and follower from the left side. To reassemble the magazine, reverse the order of the disassembly instructions.