I inherited some burton mittens from my brother in law who has given up shredding
Anyway the removable inner part was thin and crappy so I use fingered thicker inner gloves from my Mizuno gortex gloves.
Works out great waterproofing is solid and super warm. They are nice and long perfect in deep pow which is abundant where I ride (Japan).
Seems others also found what they want with this type of combo.
Only down side is no goggle wiper.