Reusable Pyrex® Mohr pipets are calibrated to Class A tolerances in accordance with ASTM E-542, and ASTM E-1293. Each glass pipette is individually serialized and supplied with a certificate of identification and capacity, traceable to NIST standards. Pipettes are designed to deliver (TD) total capacity without blow-out. Easily identify size by the color-coded graduations enameled into the glass.