First impressions? The Cheffort O2 meter feels surprisingly compact and lightweight—perfect for tossing in a backpack for climbing trips or keeping in the car for safety checks. The LCD screen is clear, and the dual-alarm (sound + light) is loud enough to grab your attention in noisy environments.

But here’s the catch: accuracy is hit-or-miss. Testing it at sea level, it read 20.9% O2 (correct), but some users report wild inconsistencies—like failing to calibrate after just a few uses or maxing out at 25% (useless for testing oxygen concentrators). Mine worked fine... until it didn’t. After 6 months, the screen froze mid-use.

The rechargeable battery is a pro—no scrambling for AAs! But the UI? Clunky. Buttons feel stiff, and navigating settings isn’t intuitive. Also, support ghosts you when issues arise (learned that the hard way).

Verdict: Decent for short-term or casual use (e.g., checking car cabin air), but if you need reliability or high-range measurements, invest in a pricier model. This one’s a $60 gamble.