Patagonia's old Capilene. I think it would be used as a mid-layer, not a base layer. The color is green, but it's a more subdued color than in the image. There's some slight pilling, but it shouldn't bother you unless you're very particular. Think of it as a slightly thinner version of the current R1 Thermal. Flat measurements: Length: Approximately 69cm Width: Approximately 53cm (at the armpits)