they are hyped as "German engineered, 95% blah, blah, blah...or 95% Specular Enhanced Aluminum, or open specular reflector...etc." They are mylar (mirror) like. The 2-T8 lamp 4' fixtures I have use these reflectors. At the time, 12 years ago, the cost of the "T12 to T8 upgrade kit" (ballast, sockets and reflector) was like $90 ea, mostly because of these reflectors. I don't think you can buy these without the fixture, but these reflectors don't seem to add to the cost of the fixture like they used to.