620 and 120 are the same film (emulsion and paper), but use different spools. You can respool 120 onto 620 spools. check out this site. http://personal.cfw.com/~cdwilcox/F_620.html
Exactly correct! (Thanks Blurmore) Hold onto your old 620 spools. The 620 spools are disappearing from the planet.:uhoh Re-spool back to the 120 spools for commercial processing. Which camera? ziggy53