Ultra Lightweight Cushion Level socks barely have any cushion level at all and are designed to create a barrier for the feet against footwear or over-socks. Consider these as a true second protective skin for your feet.
Lightweight Cushion Level Socks are slightly more substantial and more akin to the kind of socks you might wear on a daily bais to work etc. Usually with some technical structure especially to the foot welt for stability and support but still light enough to wear below heavier weight walking socks.
Midweight Cushion Level Socks have a more substantial structure with strategic cushioning at the key contact points of the foot to help eliminate contact sores, blisters and hot spots. Usually applied to hiking socks or ski socks where some cushioning is required. Socks of this nature often have a structured foot with a defined welt for added comfort and foot support. Also applicable to some sports socks such as cotton socks for tennis with padded footbed
Heavyweight Sock Cushioning Level for the extreme hiking socks and where high warmth and volume are required. Used often with high wool content socks such as Merino Wool and where extreme weather and terrain situations are likely to occur. Mountaineering and endurance walking socks usually have a heavyweight cushioning level.