The Workhorse™ Pac Boot Liner is a form-fitting, quick-drying 4-layer liner for added protection in the Workhorse™ Pac Boot. It is moisture-wicking and form-fitting for superior comfort and protection. A Pac Boot is a boot with a removable lining to add warmth in extreme cold. When choosing a pac boot, consider: the height that you want, if you need waterproof or water resistant and the right temperature range for your environment.