A slip (6108) is an undergarment worn beneath outer clothing, typically made of lightweight fabric with minimal structure. A dress (6104) is an outer garment. The key factors are the garment's weight, opacity, construction finish (raw or lace-trimmed edges versus structured hems), and whether it is designed to be seen or concealed. CBP rulings on slips versus dresses focus on these design and marketing characteristics.

Pajama sets presented together for retail sale and made of the same fabric classify as a set under the nightdress and pajama subheadings (610831–610839), with the fiber content of the chief weight determining the specific subheading. If the top and bottom are sold separately or differ in fabric, each piece is classified individually. Retail packaging and presentation at importation are key evidence for set classification.