Meta’s engineers developed ultra-narrow steel-can batteries for smart glasses like the Ray-Ban Meta and Oakley Meta Vanguards, which need to power cameras, speakers, AI workloads, and a display within the glasses’ temple arms. Traditional pouch cells were unsuitable due to wasted volume and tolerance issues. Meta’s steel-can cells, with widths as narrow as 7mm, use die-cut stacked electrode layers instead of a wound “jelly roll,” resulting in lower impedance to avoid brownouts during simultaneous tasks like recording and AI queries. The cell holds its shape to roughly 100 microns, providing usable volume for energy density. From Gen 1 to Gen 2 of the Meta Ray-Ban, cell capacity grew from 160 mAh to 210 mAh — roughly a 30 percent bump — but the product shipped with claims of double the runtime, achieved through system-level efficiency improvements rather than chemistry changes. The Oakley Meta Vanguards feature a battery in each temple arm, with symmetric cells but uneven electronic loads between the two sides.