Burettes are calibrated in accordance with ASTM E-542. Tips are carefully drawn from accurate bore tubing to ensure proper drainage rates. Burettes have colored markings, fine sharp lines, and large, easy-to-read numbers. The stopcock barrel has a smooth micro-finish to assure leak-resistant performance. Each burette is supplied with a dust cover, and all sizes are furnished with a 2-mm bore stopcock plug. Colored scale, Class A, PTFE stopcock plug Capacity tolerance on these burettes is established by ASTM E-287.