This is the 3 round Browning X-Bolt Long Magnum fit magazine, which fits the following calibres:
- .338 Win Mag (Winchester Magnum)
- .300 Win Mag (Winchester Magnum)
- 7mm Rem Mag (Remington Magnum)
Manufactured from a tough polymer the rotary X-Bolt magazine design feeds with single stack reliability while retaining a flush fit.