Manufactured with top quality 3.3 borosilicate glass and calibrated to deliver (TD, Ex). The batch number is printed on each burette. In compliance with ISO 385 and USP. The conformity with “Eichordnung” (the German Federal Weights and Measures Regulations) is certified through the official “DE-M (year)” sign on each burette. Batch certificate included (to be downloaded free of charge here)