I have some EE Torid mittens, but they are not super warm. I don’t remember which insulation thickness I got.
With the current cold weather, I have ben able to verify that I (often) need <u><i>very</i></u> warm mittens. (Raynaud’s).
I have been happy with the warmth of my Hestra Primaloft Extreme Liners.
I can’t find specs on the fill thickness, but these mittens are thick!
However, they are not very articulated, and they are a pure liner: no grip material on palm, and no closure or elastic around the wrist.
On the other hand, for liner mittens, they are overbuilt material wise: fleece liner fabric and not very lightweight outer shell fabric.
This means you need to wear a separate shell, and by then, the weight has really crept up.
Does anyone know of a light weight , but very thick mitten?
Strongly prefer synthetic, since the total amount of fill is minimal, I think the weight savings of down are small. Also, it’s hard to keep down from creating cold spots in a mitten.
Mittens also see a lot of moisture, both from perspiration and from outside.

