Works on G3 and HK91 twenty round magazines.

G3 and HK91 10/20 Block for 7.62x51mm or .308 magazines.

To Install:
This new design is held to the spring by removing the locking plate and installing the spring into the hole in the block as seen in the photo. The block and spring is then inserted back into the magazine. The locking plate is then positioned under the block. Then slide the floor plate closed as normal.

No external modifications to the magazine are necessary.