I would say it runs a hair bigger than the core light weight. I wear a Large in core lt weight hoody and large in the merino 120 hoody was slightly bigger. I went to a medium though and it was to tight in the shoulders so back to Large.how is the sizing on this hoody? I usually wear a large tall core light hoody, i remember sitkas old old merino i needed an XL. I like that tall version just for sleeve length.