This is the Steyr Mannlicher Model M 5 round factory rotary magazine in 5.6x57 for rifles with the new style dual side lock magazine.
The rotary magazine design is flush fit to the stock and is made of a tough polymer with a clear viewing plate at the rear.
Brand: Steyr
Weight: 50 Grams
Calibre: 5.6x57
Capacity: 5
Model fit: M
Material: Polymer
Colour: Black
Item Nr.: 102-2300050510