Comes standard with flush-fitting 10 round mags and can likely use any magazine made for the 10/22.
The 77/22 will accept the magazine from a 10/22, but the bottom of the 10/22 magazine has a slightly different shape. The 77/22 magazine is flat, and the 10/22 magazine is slightly curved. Not a big deal, but it felt funny enough to me to buy the correct mag.