These pipettes are made from borosilicate glass in compliance with ASTM Specification E438, Type I, Class B glass requirements. They are calibrated ''to deliver'' (TD) with blow-out after free flow of liquid has ended. Plugged and sterile pipettes are designed from ASTM Specification E714. Sizes 1 and 2 mL are packaged 25 pieces per bag, sizes 5 and 10 mL are packaged 10 pieces per bag; bags are color coded. Pipettes have negative graduations to increase versatility