FAL METRIC 10/20 rounds
Tested with magazines like the one pictured (metric, not sure what brand/origin). Email me if you want more pictures of the magazine to make sure it'll work in yours.
Limits the capacity of the magazine to 10 rounds by sitting between the base of the spring and the locking plate (see picture 3).
3D Printed - Color may vary depending on which i have currently set up in the printer.