FAQ · Power
18650 vs 21700 — which should I buy?
Buy the cell your light takes; they are not interchangeable. If you are choosing a light, a 21700 holds roughly 30–50% more capacity for meaningfully longer runtime and higher sustained output, at the cost of a slightly fatter body. An 18650 light carries a touch slimmer. For most people the extra runtime of a 21700 is worth the girth.
Related questions
Reader favorites
The short list — full rankings live on the best-gear page.
Nitecore UI1 charger + 18650
$11.99
Check priceStreamlight MicroStream USB
$42.79
Check priceZebra F-701 pen
$22.60
Check price
Straight disclosure —some links on this page are affiliate links. As an Amazon Associate we may earn a commission when you buy through them, at no extra cost to you. It never changes the price you pay, and it never changes a verdict.
63 guides published
42 products vetted
1,778 reader price checks
Featured merch
Original graphics, made to order. Gear-room aesthetics, no logos shouting.
