18650 vs 21700 Battery Cells in Power Tools
18650 and 21700 are standard cylindrical lithium-ion cell sizes named for their dimensions in millimetres — 18mm × 65mm and 21mm × 70mm — not brands or performance tiers. The larger 21700 holds more capacity per cell and sags less under sustained heavy draw.
18650 and 21700 refer to standard cylindrical lithium-ion cell sizes (18mm x 65mm vs 21mm x 70mm) used inside battery packs — not a brand or a tool spec by themselves. The larger 21700 cell packs more capacity per cell and, per cell, tends to run cooler and sag less voltage under sustained heavy draw, which is why Milwaukee's High Output line and similar 'pro' packs moved to 21700 cells for high-draw tools like saws, while smaller compact packs still use 18650 cells to stay light for everyday drilling and driving.