This T3/T3x magazine is specifically designed to suit the Lithgow LA102 & Tikka T3/T3x rifles chambered in 223 Remington, and will suit similar 223 geometry cartridges (223 see table below).A preferred choice over the factory plastic magazine for typical 2.25"-2.26" OAL factory ammo. This mag also feeds the 17 Rem, 204 Ruger and 222 Rem cartridges as standard. Also, these mags feed 221 Rem Fireball (please ask). .204 Ruger NOTE: If you are running 204 Ruger, the capacity is limited to 9 rounds (due to body shape geometry). Also, the straighter case results in a more parallel loading path, so the bullet bumps into the chamber using the internal feed ramp.