The pants are about 197 GSM. I will say the weight of the fabric isn't the only thing that makes them breathable (or not). The weave is also important for breathability as are the structure and length of the vents. I have used the Vesper in 103 degree heat, and while in heat like that I wouldn't say it feels great to wear pants, the Vespers did breathe better than any other pant I own, especially with the hip vents fully open and the fly open. FWIW, fly down and hip vents open for ventilation feels like a cheat code.I'm looking for a hot weather pant. I expect up to 110 degrees feels like temperature, lows likely no less than 80. So gsm and breathability is my top priority for this specific application.