20pcs Non-Graduated Test Tubes Laboratory Test Tool with Screw Caps Plastic test tubes for laboratory tests Round Bottom with screw caps on the top Ideal for samples, food colourings, craft use, etc. These were manufactured for use as centrifuge tubes, and hence are leak-proof. The non-wetting interior surface eliminates concave menisci, providing more accurate measurements Switching from glass cylinders to Globes plastic equivalents will greatly reduce breakage and the potential for injury