This is a factory Ruger BX-25 magazine for the 10/22 .22 lr, 25 round capacity.
The BX-25 has a maximum capacity of 25 rounds and features an angled feeding mechnism to ensure that you get the same feeding reliability as you did with the origianl 10 round rotary mag.
You can also disassemble the magazine in order to clean it, which is a major improvement on its predecessors.
