M3 Therm-X "Red Dot" reference stylus with 5.0 mm diameter ruby ball, 3.5 mm diameter carbon fiber stem, and 5.0 mm diameter x 9.0 mm long titanium base marked with a red dot. Overall stylus length is 50.0 mm. Stylus weight is 1.15 grams. Compare to Zeiss 626103-0501-050.