Recording tape cartridge

A recording tape cartridge comprising:

• a reel accommodated within a case and having a reel hub around which a recording tape is wound, an engaging portion being provided at a floor portion of the reel hub;
• a braking member, which includes a tubular portion, provided nonrotatably within the case, and approaching and moving away from the floor portion of the reel hub, and able to assume a rotation locked position at which the braking member engages with the engaging portion, and a rotation permitted position at which a state of engagement with the engaging portion is released;
• and
• a releasing member disposed so as to rotate integrally with the reel at an inner side of a guide wall portion, which stands erect at the floor portion of the reel hub, and when the reel is rotated, the releasing member holds the braking member at the rotation permitted position while abutting the braking member,
• wherein when the recording tape cartridge is in an assembled state, the releasing member, the guide wall portion, and the tubular wall portion are formed concavo-convexly when viewed from a side sectional view of the recording tape cartridge.