A cylindrical core 1 for receiving windings of a photographic film web comprises a hub 3 having an axial re-entrant channel and an insert 4 fitting into and engaging shoulders 13, 16 of that channel to define with the channel a slot 26 for receiving an end of a film web 2. Cooperating detent elements 19, 25 are provided for resisting relative axial movement between the hub 3 and the insert 4 when the latter is inserted into the channel 11, and the insert 4 incorporates teeth 24 for engaging at least one marginal perforation of a film web to prevent circumferential slippage of the film web. The slot 26 is inclined obliquely from a radial direction, and the teeth 24 are located on the inner or lower wall thereof so that the film perforations are released from the teeth when the film end is tensioned at the end of unwinding.