For a baselayer that will keep you warm on cold days, but won't overheat you in the spring, toss on the 100% Merino wool Smartwool Midweight Crew Neck Baselayer Top. The combination of Merino wool and midweight fabric provides incredible versatility; this top functions great in everything from deep winter storm cycles to year-round morning jogs. This baselayer uses the same wool that's been trusted by Norwegian whalers for a hundred years, but with flatlock seams and chafe-busting shoulder panels, it offers engineering marvels that Sven and Lars could only dream of.