Pmag 10/30 to 10/20 Magblock

How to trim a Pmag 10/30 Magblock from magazineblocks.com to a Pmag 10/20 block. Our blocks come pre-marked where to cut to be used in different types and sizes of magazines. This block will work in .223/5.56 mm Pmags. Can also be cut to fit USGI 20 and 30 round magazines and limit capacity to 10 rounds.