One suit to warm it all: Carhartt® Classic Union Suit. Waffle knit low-piling yarn traps body heat to keep you warm all over. But this isn't your granddad's union suit. Rugged Flex cotton/polyester comfortably moves with you in all directions. Adding to your comfortable wear are smooth flatlock seams, tagless label, and concealed Y-stitch waistband. And for your convenience, yes, there is a back opening. Wear this as a base layer, when camping, or simply around home on a cool day.