This is a precision probe made in accordance with UL1017 and related standards. The probe is for testing openings that have a dimension less than 1.375 in. (34.9mm). It is used to test the effectiveness of enclosures and guards. An opening in an enclosure or guard must not let any moving part be contacted by the probe. The finger is made of stainless steel and the rest of the instrument is Delrin®.