The key distinction is the tube's principal design use: a tube engineered for television reception is classified here, while a monochrome CRT designed primarily for use with computers or ADP equipment may fall under a separate heading for monitor tubes. Physical specifications such as scan frequency range, deflection angle, and connector type are the primary evidence CBP uses to determine principal use, so importers should retain manufacturer datasheets.

Residual demand comes primarily from three sources: replacement parts for legacy industrial and medical equipment that cannot be economically upgraded to flat-panel displays, specialized applications such as oscilloscopes and radar displays that historically used monochrome CRTs, and export-market resale. Importers in this niche typically deal in small, high-value lots rather than bulk consumer shipments.