18mL Glass-Stoppered test tube made from KG-33 glass tubing with a top finish to receive a ground glass joint glass stopper, and with uniform wall thickness for maximum service. Durable white ceramic enamel marking spot on each tube. Reusable. Designed from ASTM Specification E982, Type III requirements. Replacement stopper is 41900R. Capacity to Neck: 18mL. 16 x 150 (Approx O.D. x Approx. Length). Stopper Size: 13. 24-Each/Case. Kimble® #: 45100-16150.