This post is about GSS hi-viz jackets.
I considered a Carhartt winter style but saw GSS has various jackets that can be used as liners with their Onyx line of bombers and parkas. Carhartt, you get what it comes with. A stiff raincoat feeling number on the outside and a zip out fleece liner on the inside. Nice coat overall but limited in options.
The GSS line costs less and you can use the included fleece liner or zip in their hi-viz insulated hoody, or other liners that double double as a hi-viz jacket. I already had a hi-viz poly filled number from a few years back but the insulation is thin like an inner layer style.
The polar fleece liner that comes with the Onyx is toasty, but the included polar fleece liner is grabby while putting on or taking off while wearing a flannel shirt. I mean kung-fu grip grabby. So I zipped in the thin layer model jacket I already had and no more fighting the jacket.
I'd say if one were to opt for using the polar fleece liner put it on first then the outter over that. Trying to put it on or pull it off with the liner attached can be frustrating due to narrow sleeves trying to velcro to your clothes and the outter trying to come off while the polar fleece stays fastened to your clothing.
The Onyx itself is fairly warm already. It is not all "plastic" feeling in cold weather despite being waterproof. I opted for the bomber for the elastic waist band that is about the length of the parka so it is nearly as long as the parka while sealing out a cold breeze from blowing up your back where the parka has a drawstring at the belt line. And the bomber costs a little less too.
Nearly any wide tooth plastic zippered item will zip in, but the brass type or narrow tooth will not. So you aren't just stuck with GSS items for options. A nice toasty vest that came with a Carharrt rain coat for example zips right in also. I prefer wide tooth plastic zippers for bulky coats since it's so much easier to get them started in a hurry.
The only complaint I had with the Onyx is the rain hood folded up inside the collar causes the collar to stand up. While wearing a hard had it kept pushing up on the helmet adjuster knob. For a snap type helmet adjuster it's no issue but I use the quick adjust knob type to quickly size it smaller or larger depending on wearing it over a helmet liner or not. I just removed the hood, folded it up and stuck inside a chest pocket inside the Onyx. With the hood removed the collar sits flat easily.
I have a welders baklava style helmet liner that's the best $25 I ever spent. Fire retardant with 40 gram thinsulate. Put that on, then my coat over that. What cold breeze? No face mask but if I wear that a scarf goes with it for a face cover when needed.
Some pix for reference:
The Onyx ensemble;
Left is the liner jacket, right is the polar fleece jacket, bottom is the Onyx
Some Onyx details
The welders helmet liner.