A recording tape cartridge of the invention houses a reel inside a case
formed by joining together an upper case and a lower case. The reel
includes a reel hub around which is wound a recording tape, with flanges
being disposed at both axial-direction end portions of the reel hub.
Movement of the reel in the axial (vertical) direction inside the case is
possible. Upper ribs are disposed, in a radial manner coaxial with the
reel and at equal intervals, so as to vertically project from an inner
surface of the upper case opposing the flange of the upper case. The upper
ribs are disposed, in a radial shape coaxial with the reel and at equal
intervals, so as to vertically project from an inner surface of the lower
case. The upper ribs and the lower ribs are disposed so as to have a phase
difference therebetween in a circumferential direction.
