Which statement best describes Class A glassware compared with Class B glassware under ASTM standards?

• A. Class A glassware is less accurate.
• B. Class A glassware has smaller tolerances than Class B.
• C. Class B glassware has smaller tolerances than Class A.
• D. Class A glassware is more accurate and has smaller tolerances than Class B.

Answer: (B)

Tolerances are the allowable deviation from the nominal volume, and ASTM classifies glassware so that Class A must meet tighter tolerances than Class B. Because the deviation is smaller for Class A, it yields measurements that are closer to the stated value and more consistent across uses. That direct difference in tolerance is the clearest way to describe how the two classes differ, making a statement about smaller tolerances the best description. Saying Class A is less accurate would be wrong, and saying Class B has smaller tolerances is the opposite of the standard. While it's true that tighter tolerances in Class A generally lead to higher accuracy, the most straightforward descriptor of the comparison is that Class A has smaller tolerances.