Carhartt Flannel Lined clothing is slightly thicker than Carhartt Sherpa Lining. Quilted-flannel lined has the feel of a soft flannel shirt but is much warmer. It's also the 2nd thickest lining Carhartt makes for your flannel-lined jacket, flannel-lined shirt or flannel-lined jeans and pants. Carhartt flannel lined is quilted to a layer of polyester insulation for extra warmth. The flannel lining is made of flannel, as the name indicated. Not just any flannel though, Carhartt's most durable and thick flannel. This lining will ensure warmth no matter what temperature or environment you're working in.