User Review: SmartWool Women's Lightweight Zip T
Fabric: merino wool
This is an excellent light base layer, and the zip-neck adds versatility as you can unzip to ventilate if you get warm. What they say about merino wool is true--it doesn't itch, feels drier than synthetics when you sweat in it, and takes a lot longer to start smelling ripe than synthetics. Besides, at least for me, the fact that it is a natural material is appealing.
I wear mine for hiking and trail running. The fit is just right and it can be washed and tumble dried without messing that up--shrinkage is minimal. I seldom wear my synthetic base layers anymore since trying Smartwool and similar products.