I used one of those parka's while in the Alaska NG, spending many days in nights in extreme sub zero temps and wind blowing across the Bering Sea Ice.
They WORK. When cross country skiing the roll up and set on top of your pack for easy acess when you stop.
I'd recommend you get the field pants to go with them. You can find them on E-bay, along with the liners.
With the wool og shirts and pants underneith, you can stand around a long time is super sub zero temps of minus 50-60.
I left mine in Alaska, but it didn't take long in the Wyoming wind for me to find some more.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071