A simple fleece is still my used warm garment and of those I’ve tried recently the Didriksons Monte is my favourite, being comfortable and very light at 259 grams. The thin fabric is soft with a slight stretch, very breathable and quick drying. It’s not that warm, which means it’s not too hot worn under a wind or waterproof top in cool conditions. The two pockets can be used when wearing a pack hipbelt and the high collar is snug and warm. This fleece arrived 18 months ago. I’ve been wearing it regularly ever since (in fact I’m wearing it now as I write this!).