This is the ProMag Archangel 9-22 15 round .22LR magazine for the Ruger 10/22.
Made entirely from carbon fibre reinforced polymer with a stainless box spring the magazine is fully strippable for cleaning.
Bullpup stock users will appreciate the shallower curve profile compared to the Ruger BX-25 and other 'banana' magazines, which allows easy use with aftermarket bullpup 10/22 stocks such as the Muzzelite, Red Jacket and HTA chassis stocks.