I've been testing the Nano Hertz Sauna Vest for a few weeks now, and let me tell you - this thing turns your workout into a SWEAT SESSION. The polyurethane lining really traps heat like they claim. During my first HIIT class wearing it, I was dripping within 10 minutes (and not just from the exercise!).

The sizing is definitely tricky though. I'm 5'6", 150lbs with a 34C chest and got the Medium based on reviews - it fits snug but not uncomfortably tight. The armholes do run large like others mentioned. Pro tip: SIZE DOWN if you're between sizes unless you want extra room in the chest area.

What surprised me most was how lightweight it feels despite being thick material. Unlike old-school sauna suits that feel like wearing a trash bag, this moves with you during squats and doesn't roll up. The tummy control panel gives nice smoothing without restricting breathing.

Now for the cons: After about 5 washes, mine has started loosening slightly (though still functional). Also, that "increased VO2max" claim? Maybe after months of use, but don't expect instant cardio gains. And fair warning - the low-cut design shows serious sports bra cleavage!

Verdict? If you want to amplify sweat during workouts and don't mind playing sizing roulette, it delivers. Just manage expectations - it's a sweat booster, not a magic weight loss solution.