Two headlamps worth lining up side by side. They score within a hair of each other, so it comes down to the details below.
| Black Diamond Cosmo 350 | Black Diamond Astro 300 | |
|---|---|---|
| GearScore | 73✓ | 72 |
| Max lumens | 350 lm✓ | 300 lm |
| Weight | 2.7 oz | 2.6 oz✓ |
| Beam distance | 70 m✓ | 55 m |
| Max runtime | 200 h | 140 h |
| Price | $30 | $20✓ |
| Battery | AAA | AAA |
| Water rating | IPX8 | IPX4 |
Highlighted cells mark the better spec: Cosmo 350 in blue, Astro 300 in amber. A blank spec is never counted as a win. Runtime is shown for context and is not scored, since makers publish it at different brightness levels. GearScore is the overall rating (0 to 100); re-weight it on the full headlamp comparison. Prices are current MSRP.
The Black Diamond Cosmo 350 and Black Diamond Astro 300 take different routes to the same job. They are close enough that this really is about which handful of specs you weight most.
The Cosmo 350 is brighter (350 vs 300 lm) and a longer beam (70 vs 55 m). The Astro 300 is a little lighter and $10 cheaper. Their GearScores land within a couple of points (73 vs 72), so neither runs away with it.
Pick the Cosmo 350 if you care most about brightness and longer throw, which makes it the better call for your priorities. Pick the Astro 300 if low weight and price matter more to you, or you are focused on counting grams on long miles.
The Black Diamond Cosmo 350. It is brighter (350 vs 300 lm) than the Astro 300.
The Black Diamond Astro 300. It is a little lighter than the Cosmo 350.
They are nearly tied at 73 and 72 on the default algorithm, so re-weight the score to your own priorities to break the tie.
It depends on your priorities. Go with the Cosmo 350 for brightness, or the Astro 300 for low weight. The spec table above shows exactly where each wins.