This special light source is designed for use with all types of speculums in goat artificial insemination. Sub-miniature bulb at end of narrow plastic tube puts light where you need it: directly on the cervix. Lies flat against the side of speculum. Small so it will not interfere with vision. Designed by people who work with goat A.I. regularly, light source is very convenient to use. Needs one 9-volt battery (not included).