Vintage US M51 Field Pant Liners *Rare*U. S. Military pant liners. They are made to fit inside the M51 field combat pants. They have buttonholes at the waist and button closed at the center front. They are olive drab nylon interior with cream colored frizzae wool on the exterior of the liner, which is used asa very warm protectant. It is tightly woven and an abrasive hand. It's rough texture keeps its strength in the winter weather while keeping the warmth from the wool inside.