Convoy M21B vs Olight ArkTac Ultra size comparison
The Olight ArkTac Ultra is 5.9 mm (0.23 in) shorter than the Convoy M21B, and 6.7 mm narrower at its widest point. Weights are published on different bases (with battery vs listed), so compare them with care.
The Olight ArkTac Ultra is 5.9 mm (0.23 in) shorter than the Convoy M21B, and 6.7 mm narrower at its widest point. Weights are published on different bases (with battery vs listed), so compare them with care.
Dimensions
| Convoy M21B Check price ↗ | Olight ArkTac Ultra Check price ↗ | |
| Length | 141.5 mm (5.57 in) | 135.6 mm (5.34 in)−5.9 mm |
| Head / width | 35.7 mm (1.41 in) | 29 mm (1.14 in)−6.7 mm |
| Body | 27.1 mm (1.07 in) | — |
| Thickness | — | 17 mm (0.67 in) |
| Weight | 120 g listed | 140 g with battery |
| Battery | 21700 | Built-in |
| Max output | — | — |
| Throw | — | — |
| Type | EDC | EDC |
| Price | $48.99 at flashlightgo.com, as of Nov 4, 2026 | $159.99 at olight.com, as of Nov 4, 2026 |
| Source | flashlightgo.com sourced Output depends on LED option | olight.com unverified Dims from ArkTac series comparison table (row assumed to be Ultra); re-check on ArkTac Ultra page |
We may earn a commission from these links, at no cost to you. Rankings are never paid for. Disclosure
M21B vs ArkTac Ultra: how they differ
Size and weight
The Olight ArkTac Ultra is the shorter light: 135.6 mm (5.34 in) against 141.5 mm (5.57 in), a difference of 5.9 mm (4%). At its widest point the Olight ArkTac Ultra is 6.7 mm slimmer (29 vs 35.7 mm). Weights are published on different bases (Convoy M21B: 120 g listed; Olight ArkTac Ultra: 140 g with battery), so they are not directly comparable.
Brightness and throw
Output for the Convoy M21B depends on the LED option chosen.
Battery
The Convoy M21B runs on a removable 21700 battery; the Olight ArkTac Ultra runs on a built-in rechargeable battery. Only the Convoy M21B lets you swap in a charged spare.
Price
When we checked on Nov 4, 2026, the Convoy M21B was $48.99 at flashlightgo.com and the Olight ArkTac Ultra $159.99 at olight.com, so the Convoy M21B cost $111.00 less. Prices change often, so check the current price before you buy.
Type
Both are EDC lights in our catalog.
Which should you buy?
Choose the Convoy M21B if you want a removable cell you can swap. Choose the Olight ArkTac Ultra if you want a shorter light (5.9 mm shorter), a slimmer profile (6.7 mm narrower) and a built-in battery with no separate cell to buy. We compare published size, weight, output, throw and battery only, not runtime, interface or build quality.
Check price ↗ Convoy M21B Check price ↗ Olight ArkTac Ultra
We may earn a commission from these links, at no cost to you. Rankings are never paid for. Disclosure
M21B vs ArkTac Ultra FAQ
Which is smaller, the Convoy M21B or the Olight ArkTac Ultra?
The Olight ArkTac Ultra is the shorter light: 135.6 mm (5.34 in) against 141.5 mm (5.57 in), a difference of 5.9 mm (4%). At its widest point the Olight ArkTac Ultra is 6.7 mm slimmer (29 vs 35.7 mm). Weights are published on different bases (Convoy M21B: 120 g listed; Olight ArkTac Ultra: 140 g with battery), so they are not directly comparable.
Which is cheaper, the Convoy M21B or the Olight ArkTac Ultra?
When we checked on Nov 4, 2026, the Convoy M21B was $48.99 at flashlightgo.com and the Olight ArkTac Ultra $159.99 at olight.com, so the Convoy M21B cost $111.00 less. Prices change often, so check the current price before you buy.
Do the Convoy M21B and Olight ArkTac Ultra use the same battery?
The Convoy M21B runs on a removable 21700 battery; the Olight ArkTac Ultra runs on a built-in rechargeable battery. Only the Convoy M21B lets you swap in a charged spare.
Compare Convoy M21B with similar lights
Compare Olight ArkTac Ultra with similar lights
More
Sources
- Convoy M21B: specs from manufacturer published specs as listed by flashlightgo.com. Drawing: outline from published specs. Price $48.99 from flashlightgo.com, checked Nov 4, 2026; prices change often.
- Olight ArkTac Ultra: specs from Olight product page (manufacturer). Drawing: shape measured from manufacturer photo (olight.com), scaled to the published length and diameter. Some values could not be confirmed on a second source and are marked unverified. Price $159.99 from olight.com, checked Nov 4, 2026; prices change often.
Found an error? Email liambuehlerbusiness@gmail.com and we will fix it.