Tubes specially designed for checking the surface tension of liquids. Each tube is accurately calibrated to help quickly determine surface tension by the drop count method. Each tube is graduated above and below the bulb. Tubes are available in 2.5 ml, 3.5 ml and 5.0 ml sizes. The 2.5 and 5.0 ml sizes allow flexibility in sample size, while the 3.5 ml size is used for more viscous applications. Supplied in a set of 3 tubes (1 of each size) in a protective plastic case, with instructions for use.