If you are constantly searching for the right light source to read a refractometer, you may want to upgrade your current refractometer to utilize a LED illuminated prism cover. The cover has a built-in LED light that will give you consistent readings and never leave you without proper light to take a reading. Installing the LED Cover only takes a minute, just loosen the set screw on your current cover, slide it off the refractometer and slide on the new one. Once the new cover is on, just press it down against the prism and tighten the set screw.