No idea! The shirt is fairly heavy-weight and a very warm, yet breathable, base layer.
I'm not sure and I've thrown out all the tags, etc. but it's 260 weight, at least by Icebreaker and I will tell you that it's significantly thicker and heavier than their everyday bodyfit 200 weight. Those are a good layer in themselves but this shirt is quite warm and still soft and not very scratchy at all. Today I wore it with an Icebreaker 260 sierra cardigan and a very thin Marmot Minimalist Gortex SCR jacket. On bottom I had the 260 weight Icebreaker leggings and the Marmot Minimalist goretex pants. I was toasty riding my mountain bike in 32 degree weather with mix sleet and snow coming down heavy all over town for like 10 miles. Not a shiver. and not a bit of odor or perspiration accumulated inside. Went to yoga on the way, got sweaty, put the gear back on and was bone dry for the uphill climb back home.
I've used the same layers for biking in under 20' weather last week. Nice pair of goretex ski gloves with cuffs and a nice warm fleece hat and I was totally tight. Hit some massive uphills that day and just got kindled inside. Got out at the appointment and was not even real sweaty. smelled ah-ight.
Washes pretty well too but you don't have to very often. a little bit of Dr. Bronner's almond castille in a foot basin or bucket of luke warm water once in a while and you're good.
don't know the answer to this,but it is a great shirt
"...but it's 260 weight, at least by Icebreaker "
260 is good enough for me. ;)
"...a little bit of Dr. Bronner's almond castille in a foot basin"
Haha. good enough for the skin, so good enough for the garment although i am just a tad concerned about the perfumes used. They can be a general term used for hiding all kinds of stuff.