Abstract: Each section (1) of a drill pipe string carries a substantially annular protector (2) that is movable in a freely rotatable manner around (4) the longitudinal axis of the section (1) concerned. Each protector (2) is also movable lengthwise (3) throughout the length of the section (1) between junctions at its opposite ends or to an extent that is limited by retaining rings secured in appropriate positions around the section (1). Each protector (2) is formed from a relatively hard material having a very low co-efficient of friction, such as polytetrafluoroethylene, and is advantageously produced in two separable halves (FIG. 3) to facilitate embracing assembly around, or quick removal from, the co-operating pipe section (1). If necessary, the protectors (2) may be formed throughout their axial thicknesses with flutes significantly to reduce the fluid flow constraint produced by the presence of the protectors (2).