Section 241.4 - Application of tolerance for "diameter of head."(a) The tolerance established in this part for the dimension specified as "diameter of head" shall be applied to the diameter of the head over all, including the part which fits into the croze ring of the completed barrel.(b) The tolerance established in this part for the dimension specified as "effective diameter of head" shall be applied as follows on the various types of barrels and subdivisions in use;(1) When a barrel or subdivision thereof has two heads, the tolerance shall be applied to the mean of the average diameters from inside to inside of staves at the inner edges of the heads.(2) When a barrel or subdivision thereof has but one head and a croze ring or other means for the insertion of a head at the opposite end, the tolerance shall be applied to the mean of the average diameters, one taken from inside to inside of staves at the inner edge of the head, the other from inside to inside of staves at the inner edge of the croze ring, or from inside to inside of staves at a point where the inside surface of a head would come were such head inserted in the barrel.(3) When a barrel or subdivision thereof has but one head and no croze ring or other means for the insertion of a head at the opposite end, the tolerance shall be applied to the mean of the average diameters, one taken from inside to inside of staves at the inner edge of the head, the other taken from inside to inside of staves at a point 11/8 inches from the end of the staves in the case of a barrel or 3/4 barrel, or at a point 1 inch or 7/8 inch from the end of the staves in the case of a 1/2 barrel or 1/3 barrel, respectively.(c) The standard allowance for depth of croze ring shall be 3/16 inch. Therefore, the standard "effective diameter of head" in the case of the standard barrel is 163/4 inches and in the case of the standard cranberry barrel is 157/8 inches.