A hair curler or roller (1) consists of a cylinder of plastic such as polyamide with two end rings (4) joined by longitudinal ribs (5). A pair of pistons (2) with piston rods (3) slide inside the cylinder (1). The end face of each piston has a number of slender spikes (7) equally spaced around its periphery. The spikes (7) point forwards and radially outwards. There are as many spikes (7) on each piston as there are slots (6) between the ribs (5). The pistons are arranged so that one spike from each piston projects through one slot (6). The pistons are withdrawn to the end rings (4) and a lock of hair is wound round the cylinder. The pistons are then moved towards each other so that the hair is clamped in the slots and cannot unroll.