A lockable shopping cart wheel (10) comprises a plastics hollow casing (12), an axle (22) on which the casing is rotatably mounted and a resetable locking mechanism that is mounted on the axle in the casing. The casing has an end wall (14), a cylindrical wall (16) having a tire (20) and an end wall (18). The locking mechanism includes a locking plate (34) which is axially displaceable but rotationally fixed to the axle (22). A coil spring (38) acts between wall (18) and plate (34) urging it towards wall (14). The plate (34) defines formations which can engage the wall (16) thereby locking the wheel. Between the plate (34) and wall (14) are three gear wheels (44.1), (44.2) and (44.3) which meter the number of revolutions of the casing and release the plate (34) when a predetermined number of revolutions has taken place. The plate (34) is ferromagnetic, allowing the plate to be displaced against the spring action to reset the locking mechanism by using a magnet from outside the casing.