Decitex measures yarn fineness — a lower decitex indicates a finer, sheerer yarn. Subheading 611521 covers pantyhose and tights of synthetic fibers with a yarn fineness under 67 decitex (sheer hosiery), while 611522 covers those at 67 decitex or more (heavier-weight tights). The distinction affects both duty rates and quota eligibility under certain trade programs, so accurate yarn-count documentation from the mill is essential.

Graduated compression hosiery is specifically engineered to exert measurable, calibrated pressure that decreases from the ankle upward, typically expressed in millimeters of mercury (mmHg). Standard support hosiery with general elasticity does not meet this technical definition and classifies under the appropriate fiber-based subheading. Importers claiming 611510 should have technical specifications confirming the graduated compression profile.