The crushing strength of various models of cemented tungsten carbide pistons has been determined as a function of the ratio of unconstrained length to diameter (L/D). There was little effect for pistons whose ends were unsupported, but a dramatic increase in crushing strength with decreasingL/Dfor pistons whose ends were supplied with interference‐fitted binding rings. Tests with pistons of different diameter but constantL/Dsuggest the absence of any effects dependent on the diameter of the pistons.