What is Mrs Fletcher making Tom to give Willie on his birthday?

Mrs. Fletcher is knitting Willie a "balaclava" (warm, head covering) for his birthday.

Willie turned to find the Fletchers with two of their sons moving into their pew. Mrs. Fletcher leaned towards them. "Mr. Oakley," she whispered, "I begun the balaclava." Tom frowned her into silence. It was Willie's birthday on Thursday, and he wanted it to be a surprise.