- If Thins exceed the limit for U.S. No. 3, does the sample grade a U.S. No. 4 or Sample grade?
ANSWER. U.S. No. 4. The factor “thins” is a limiting grading factor for U.S. No. 1, 2, and 3 only. Consequently, samples containing more than 25% thins (maximum limit for No. 3) would receive a U.S. No. 4 designation.