KRISS USA has KRISS MagEx 25+ Extension Kit for Glock 21 magazine available. This extension adds 12 rounds to standard Glock 21 magazine, making it 25 rounds total.
Price: $35.99
Link: https://kriss-usa.com/shop/products/kriss/magazines/magex-25-extension-kit-for-glock21
From: Soldier Systems
