These Pyrex® volumetric pipets were designed primarily for schools and laboratories where the Class A tolerance of the Cat.No.1-7100 series is not required. They are constructed to the same wall thickness and length as those pipets, but have larger tip openings for faster delivery. It is primarily due to this faster delivery that accuracy tolerances are twice those specified for Class A volumetric ware. Sizes 0.5mL through 25mL are color-coded. Reference: ASTM E-969.