Nessler tubes, also known as colorimetric tubes, are laboratory glassware designed for measuring and comparing liquid samples in color-based analytical tests. Made from durable borosilicate 3.3 glass, they provide clear visibility and precise volume markings, enabling accurate observations in quantitative colorimetric analysis. Available in stoppered and non-stoppered variants, and compatible with racks and holders, Nessler tubes are widely used in water testing, environmental monitoring, research, industrial and teaching laboratories.