premise: In Chicago , some time ago , Mr. H. , age 27 , a diabetic since he was six , stopped using insulin because he had bought a `` magic spike '' - a glass tube about the <mask> of a pencil filled with barium chloride worth a small fraction of a cent - sold by the Vrilium Company of Chicago for $ 306 as a cure-all .
hypothesis: the proper context for <mask> here should be the physical magnitude of something (how big it is)