Larger/longer sights, like our 30mm Red Dot Sight and 30mm Red Dot Multi Reticle, sometimes require different mounts to accommodate your needs. These mounts are most commonly referred to as Cant or non-Cant mounts. Canting is simply moving the optic forward a bit in order to allow room for a magnifier on rifle with limited rail space. If your rifle's real estate is not a problem or you do not plan on using a magnifier, you will be fine with a non-canted mount. You can upgrade to a canted mount at any time (just be willing to pay for an additional mount and re-zero your optic). If you think you might want to add a magnifier to your rifle and your space is limited, you will probably want to buy the canted mount to be safe.