These reusable 5mL PYREX pipets are calibrated to Class A tolerances in accordance with ASTM E-542, and ASTM E-1293. Each pipet is individually serialized and supplied with a Certificate of Identification and Capacity, traceable to NIST standards. Calibrated "to deliver" (TD) their total capacity without blow-out. Color-coded by size for easy identification. Colored graduations are enameled onto the glass. The top end is constricted (Mohr type).