The Alangator TriMag requires three standard Ruger 10/22 magazines. Extended magazines, or magazines with alternatively styled baseplates will not lock in place.
Don't take any chances looking for an extra magazine. The TriMag locks 3 factory magazines into a triangular shape, without any modification to Ruger factory magazines. As an added benefit, different types of ammo can be loaded and kept ready, but separate, for different types of small game.
The patented TriMag design does not require any glue or adhesive, it only requires a standard screwdriver or coin to assemble/disassemble in the field or home.
Note: Magazines not included