Kirk Stierwalt Neck Sweat System with SBR Neoprene Liner - Large - Black The most versatile neck sweat system on the market! The black Flex Foam liner retains heat for the perfect sweat while the easy-to-clean channels trap dirt and grime to eliminate buildup on the skin. The innovative neck sweat system features a durable black harness leather shell with a Flex Foam replaceable liner secured in place with heavy-duty hook and loop closures. Nickel-plated hardware.