I use all of the Sitka gear. I layer depending on outside temp. The only other product I use in combination with it when it’s real cold (Montana, 3 to 6 degrees, my coldest hunt on stand) is merino wool underwear, wool socks and insulated rubber boots. I am good to go for up to 5 or so hours on stand. I like Sitka stuff. It's lite and tough and for me it’s warm. It is also easy on, off and fits in my day Pac with ease.
In order
1 merino wool or Traverse or Expedition Bottom and Top (sometimes both wool and Sitka)
2 Traverse Zip Tee
3 Vest (older Sitka lined)
3 90% jacket or Kelvin jacket depending Temp
4 wool scarf and wool hat
5 Gloves
I can't sit forever, just my nature. This system allows me (I sweat, big-time!!) to add and subtract layer as needed and still not feel the bulk.
I also use the light weight stuff in the warmer months.
I love this stuff.