Abstract: A thermal transfer ribbon cassette comprises a supply (1B), a take-up spool (1A) and a molded casing (10); each spool having end portions (2, 3) and a bobbin portion (4) on which is wound one end of the transfer ribbon (5), the molded casing having locating (15, 16) means for engaging the spool ends while the spools are in parallel and spaced apart positions with the transfer ribbon extending between them, and means to retain the spool in such position comprising a closable gate (30) connected to the casing by an integrally molded hinge (31). Locating means for engaging a spindle at the undriven end of each spool, suitably comprises a trough having an internal bearing surface and a longitudinal opening (27) to receive the spindle into contact with the bearing surface, the gate (30) being closable across the trough opening to retain spindle (3). This permits a simple design for a relatively cheap, one-piece molded casing, which can be refillable if required.