Merino wool no if's or and's. By far the best. Especially if you're on a trip where you can't wash them after each use or do anything where you'll sweat or get wet. Synthetics will stink after a use or two and loose their warmth when wet. I like Patagonia merino wool items, but I know other companies have good products as well. My Patagonia ones have numerous times been accidently put in the dryer and not been destroyed at all. Before trying their Merino wool base products I'd always found wool way too itchy for me to wear. But their Merino wool products don't itch a bit and last forever.