Opticsplanet.com sells the Bushnell Holo 510021 as a PISTOL scope - whereas the 510023 is sold as a RIFLE scope. Both seem to have the same specifications... e.g., length, weight, reticle, etc. Bushnell.com does not even list the 510021 -- listing only the 510021 and the 510023AP, which is am "AP Camo" model (instead of the standard "black").