Precision bore tubing is used in these Class A Pyrex® burets to assure accuracy between any two points. Durable colored graduations are sharply defined and easy to read. Carefully ground ST stopcock gives precise control. All sizes furnished with a 2mm bore stopcock plug. For replacement Pyrex® stopcocks, see No. 1-7680. For replacement retaining clips, see No. 1-7280. The capacity tolerance on these burets is established by ASTM E-287 and is calibrated in accordance with ASTM E542. Each buret is supplied with a dust cover.