Patent ID: 6857592

Claim:
A recording tape cartridge comprising: a case formed by joining together an upper case and a lower case; a reel that includes flanges respectively disposed at both axial-direction end portions of a reel hub wound with a recording tape, the reel being housed in the case and rising and being rotated inside the case when the recording tape cartridge is used; plural upper ribs disposed, in a radial manner coaxial with the flanges and at substantially equal intervals, so as to vertically project from a surface of the upper case opposing the flanges; and lower ribs disposed, in a radial manner coaxial with the flanges and at substantially equal intervals, so as to vertically project from a surface of the lower case opposing the flanges, with the number of lower ribs being equal to the number of upper ribs, wherein, when the upper case and the lower case are joined together, the upper ribs and the lower ribs have a phase difference therebetween in a circumferential direction.