Shadowless bottom transmits undistorted light. There are no dark spots when the tube is filled with liquid and viewed from the top using a light source beneath the tube. Used to determine the color of refined vegetable oils, such as cottonseed, corn and soybean oils, and also tallows, greases, fatty acids, etc., with Wesson type tintometers (AOCS Method Cc 13b), and of whole and refined tall oils with a Lovibond tintometer. Rings and legend are durable white ceramic enamel. Rings are located at specific distances from the inside bottom of the tube. Manufactured from 33 expansion, low extractable borosilicate glass conforming to USP Type I and ASTM E438, Type I, Class A requirements.