We'll admit - we seriously geeked out when designing this sock. Our goal was to create the perfect fusion between boot and sock. The result was the Function 5. We worked closely with boot fitters to dial in five precisely located comfort pads that diminish pressure points for the ultimate fit. Shin padding protects from "shin bang" while Achilles padding reduces heel lift. We even developed a pad zone that protects the top of the foot from second buckle pressure. Plus nothing feels better than the warmth Merino Wool provides when the mercury drops. If you're a sock geek you'll love the attention to detail we put into this sock. Still made in Vermont. Guaranteed for life.