Made of top quality 3.3 borosilicate glass. In compliance with ISO 4788, USP and “Eichordnung” (the German Federal Weights and Measures Regulations). The conformity with “Eichordnung” is certified through the official “DE-M (year)” sign on each measuring cylinder. Calibrated to contain (TC, In). Each measuring cylinder has a batch number printed on it. Batch certificate included (to be downloaded free of charge here)