M3 stylus with 4.0 mm diameter ruby cylinder, 2.0 mm carbide stem, and 4.0 mm diameter x 7.0 mm long stainless steel base. Overall stylus length is 40.0 mm. Stylus weight is 2.20 grams. Cylinder styli are used for probing narrow edges, like those found on stampings and sheet metal. They are not suitable for high accuracy work because the form of a cylinder is not as precise as a sphere. Please contact Q-Mark with any questions about calibrating or using cylinder styli.