SmartWool running crew is ideal for warm, sunny hauls. Light half cushion construction provides a barrier on heel strike, while 4 Degree Fit System uses various elastics in the sock for greater stretch and assistance keeping the sock in place within your shoe. Achilles pad eliminates abrasion at heel. SmartWool construction with 70% merino wool, 28% nylon, and 2% elastane. Overall 3.75" height.