This reinforcing yarn/repair yarn, made by Lang, is 75% machine washable wool and 25% nylon. Each spool is 23 yards. The best we can describe its thickness is that of heavy thread.
It can be used as a carry along when working sock heels or toes. (We recommend one spool per sock.) It can be used as a single thread for darning, or as several threads held together for a larger repair.