They are a .22 centerfire. Their bullets are .224" in diameter, same as the .223 or 220swift. Usually weight between 45-55grains. Think of them as a souped up 223. They are excellent for Coyotes, crows, prairie dogs and such. There are those you will say it will do deer. But very few of the .22 caliber bullets are designed with anything other than varmints in mind. This means they expand rapidly at the cost of nearly all penetration. I know, because I have foolishly tried. There is two factory offering I know of that uses a 'penetrating' bullet. Federal Trophy Bonded Bear Claw and Winchester makes a 60gr powerpoint CXP2 offering. ANOTHER problem is that the factory guns don't generally like bullets wieghts above 55gr. (especially remingtons, they have a slower twist)

All that is too discourage you from purchasing it as a deer cartridge. If you want it for something like coyotes/foxes/prairie dogs it's one of the finest choices out there.