Mauser Rimfire 4440016 STG-44 25rd 22 LR Black Polymer
https://www.tandktactical.com/shop/713440970962-mauser-rimfire-4440016-stg-44-25rd-22-lr-black-polymer-28773
https://www.tandktactical.com/web/image/product.template/28773/image_1920?unique=5678370
This replacement or spare magazine is compatible with your Mauser STG-44.
