Sport weight yarn is measured as #2 Fine on the Standard yarn weight system. It is often used for infant and children's wear. Gauge for sport weight yarn is usually 5-7 stitches per inch on a US 3-5 needle.
I bought alpaca socks for my husband and sons for Christmas and they all love them. They say they are the softest, warmest socks they have ever worn. My husband has diabetes and his feet are very sensitive, so it is especially lucky that I found these socks for him.