An open glass envelope is an unfinished blank—it has not been sealed, evacuated, or fitted with electrodes. Once the envelope is sealed and completed into a functional lamp or tube, it reclassifies as a finished electrical article. The open/unfinished status is therefore the defining criterion that keeps these components within the glass products heading rather than the electrical equipment headings.

UV germicidal lamps, high-intensity discharge (HID) lamps for industrial and horticultural use, quartz halogen envelopes, and specialty medical or scientific lamp tubes continue to require glass envelopes that cannot be directly substituted by LED technology. These niche segments sustain ongoing import demand even as general-service incandescent envelope trade has contracted.