A firm-grip rim includes two walls, an internal ring, an external ring and two flanges. The walls extend in an annular manner. The internal ring is formed between the walls. The external ring extends around the internal ring and includes two lateral portions connected to the walls respectively. Each of the flanges extends outward from a corresponding one of the walls in a radial direction so that there is a corner between it and a corresponding one of the lateral portions of the external ring. Each of the flanges includes an internal side formed with a grip device.