Kimax 50mL precision burette is permanently marked with an individual serial number. Supplied with a Certificate of Graduation Accuracy. Filling tube and overflow tube at the top of the burette accepts ¼" I.D. flexible tubing. Filling is through stopcock. Burette is self-zeroing style. Stopcock for all sizes is standard 2mm bore. Scale is durable black ceramic enamel. Calibrated to the accuracy requirements found in ASTM Specification E287, Class A requirements. Replacement stopcock is S6445. Kimble #: 17054F-50.