We start with a 1/8" shaft and reduce the diameter to 1/16" (1.5mm) at 1/2" from the needle tip. This gives you a compromise between durability and the better speed of a needle type probe. Used in liquids and soft semi-solids including rubber, plastics and similar materials. A complete reading takes only 4 or 5 seconds. Max temp: 482°F (250°C).