Fiber Trends design. Three children's and three adult sizes. Use worsted weight yarn to make children's sizes and bulky weight yarn to make adult sizes: Cap in worsted weight will fit children's head up to 18" (19", 21") (46 (49.5, 53) cm). Cap in bulky weight will fit adult head up to 22" (23", 25") (56 (60, 63.5) cm). Yarn Requirements: Choose a wool or other natural fiber that will felt easily. Child's cap requires approximately 130 (160, 180) yds (119 (145, 165) meters) of worsted weight yarn. Adult cap requires approximately 150 (180, 210) yds (137 (165, 192) meters) of bulky weight yarn. Suggested Yarns: Child's sizes: 10ply Wool. Adult sizes 14ply (chunky weight).