file fit rings have more ring than you need and may require file just to get them in with zero gap , from there you file to get your desired gap for each ring and for each cylinder
non file fit are rings that should have the proper gap, usually for a cheap rebuild , but i would never assume that they would be good out of box , check them in the bores and if your gaps are too tight they need to be filed to fit .. if too big a gap you may want to order a different ring set