The capacity tolerance on this Class A 50 mL PYREX® buret is established by ASTM E-287 and is calibrated in accordance with ASTM E-542. Tips are carefully drawn from accurate bore tubing to insure proper drainage rates. This buret has 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 buret is supplied with a dust cover. All sizes are furnished with a 2mm bore Product Standard PTFE (Polytetrafluorethylene) stopcock plug. For a replacement PTFE stopcock plug only, see No. 7681-2.