The receiver profile is the same for the Brno 21/22, ZKK series, ZG-47 and the newer 550 series. Be aware that most of the Brno 21/22 rifles have a flat ( butterknife) bolt handle that requires the use of high rings. I own one of those, and also one of the very rare 21H rifles with a round knob, low mounted bolt. Those can take most medium height ring mounts. Leupold compact scopes have a small ocular ring and allow somewhat lower scope mounting.
FYI, the M21 is the longer barrel version, M22 is the carbine. F= full stock H= half stock
Enjoy your new rifle! I just used my 21H 8x57IS to take a bull elk a few days ago.
