I was lucky enough to wear this Rab MeCo 165 Hoodie on a multi-day mountaineering trip in the Alps and loved it. It’s the only baselayer with a hood, and it’s very well fitting. The fabric is a mixture of 65 per cent merino wool and 35 per cent recycled polyester with 37.5 technology (formerly Cocona) that uses carbon from coconut shells to make the wicking more efficient. Whatever the technology, it’s comfortable, wicks well and dries more quickly than a straight merino top. The long zip has a big baffle so very comfortable.