We analyse the mask associated with the 2n-point interpolatory Dubuc-Deslauriers subdivision scheme S a [n] . Sharp bounds are presented for the magnitude of the coefficients a2i−1 | is comparable to i −1 , and for larger power scales, exponentially decaying bounds are obtained. Using our bounds, we may precisely analyse the summability of the mask as a function of n by identifying which coefficients of the mask contribute to the essential behaviour in n, recovering and refining the recent result of DengHormann-Zhang that the operator norm of S a [n] on ∞ grows logarithmically in n.