structural:summarization, quality:correction
Skein

Skeins are one of the most common types of yarn ball. Although skeins are technically described as yarn that has been wound into an oblong shape, the word "skein" is used generically to describe any ball of yarn. Many large-scale yarn retailers like Lion brand and parent companies like Yarnspirations sell their yarn in skeins. Unlike other types of yarn balls, a skein allows you to access both ends of the yarn. The yarn end in the inside of the skein is called a center pull. One major complaint of center pull bullet skeins is that the inside yarn end is not easily found, and often is pulled out of the skein in a jumble of tangled yarn called "yarn barf". There are two types of skeins: a pull skein, which is more rectangular in shape, and a bullet skein, which is rounder.