This bulb is a 6V 20W Halogen with a G4 Base and is used in several medical, veterinary and industrial applications. The 64250 bulb from Osram is a OEM bulb for several microscopes from manufacturers such as Swift, Nikon, Olympus, Zeiss, Bausch & Lomb and American Optical. This bulb is equivalent to the Philips brand bulb sold under part number 5761.