These closed system borosilicate glass burets help protect media from external contamination. Burets have easy to read blue graduations against a white background. The delivery end is fitted into a plastic push button stopcock which permits drop by drop delivery. A small screw clamp presets drop speed for repeat titration. A polyethylene filling tube extends from the top of the buret into the bottle reservoir. Bottle, screw cap, and round base are polyethylene. Sturdy polyethylene flanged base provides stability. Graduation accuracy is Class B. Packaged 12 per case.