I use my Furnace during all times of the year. In summer it works as an outer layer and in late season it's all I need under my puffy.

I really like First Lite Base Layer Tops and Bottoms. My one complaint is that all of the tops are way too long. The sleeves are a little long, but manageable. The main length, however, feels almost like a dress. If you're packing three or four tops, the extra weight adds up, especially with the Kiln and Furnace layers. I'm having mine altered, both for fit and weight savings. This is an added cost to an already expensive purchase. Otherwise, the tops are awesome. I love the feel of them, their odor control, their warmth, the high collars and I like having the ability to pull the zippers down for ventilation. I also love the Cipher camo pattern.

Once the real cold hits, only base layer you’ll need

The Furnace is great late-season merino, particularly for cold sits in the December and January tree stand. I've used it effectively with layering into the single digits It is super warm, so is not something I would recommend for a lot of hiking--there is lighter-weight merino for that--but for more sessile hunts, this is just the trick, particularly underneath some First Lite outer gear. Worth the money-as is everything at First Lite.

Extremely nice wool. Warm and incredibly soft. I gave 4 stars because it has a boxier cut than my other FL gear. The waste on the seem to flare a bit more than others. Even still, its one of my favorite pieces of gear. Extremely versatile for anything below 35.