You can wear these military fleece overalls underneath your snow pants or gore-tex pants. They are made of fleece and are not waterproof. You can use them as liners for waterproof pants, such as the Army issue Gore-tex Level 6 pants.
Polartec Classic 200 bibs are affordable and high quality. The classic 100% polyester velour traps air to maintain heat, increasing insulation. This non-pilling bib is perfect for outdoor enthusiasts. They hold up in less forgiving environments, such as skiing and snowboarding.
These overalls are best worn under other pants depending on the environment. For example, when you need to stay dry, level 6 extreme cold wet weather trousers. If you just need to stay warm, try the level 5 or 7 pants!