Made of top quality 3.3 amber borosilicate glass. Designed according to ISO 1042, DIN 12664 and calibrated to contain (TC, In). Each flask has a batch number printed on the flask. Batch certificate included (to be downloaded free of charge 
here)
reference: VFLA-500-002, capacity: 500 ml, accuracy (ml): ± 0&comma:250, stopper: 19/26, pcs/pack: 2