SmartWool Women's PhD Run Ultra Light Micro Socks 48% Merino Wool, 48% Nylon, 4% Elastane Knit in the USA 200 needle construction provides highest knit density while maintaining ultra light weight Virtually seamless toe - Achilles tab 1.5" overall height - Sock Height: Micro Run-specific fit - Style:SW0SW188 Machine Wash Warm Gentle Cycle. Do Not Bleach. Tumble Dry Low. Do Not Iron. Do Not Dry Clean.