What are the advantages of ruby over other materials for a ball probe tip? The most important features of a ruby that make it the top-choice material for ball probes are 1) its resistance to abrasion and 2) its resistance to compression. A naturally hard substance, ruby is particularly tough when it comes to use in precision measurement. Knowing that your ball probe will not be damaged while conducting measurements is extremely important. The level of sphericity of the ball on a ball probe is crucial to the accuracy of the measurement. Any damage or warping that occurs will result in an unreliable readout. Ruby ball probe tips have incredible smoothness and are able to combat the damages that may occur with other materials.