The Mk16 Can Seamer comes standard with a can guide for the 211 can diameter. Sleek cans are 204 diameter, which are then capable to be seamed with this can guide installed.
This can guide allows the Mk16 to seam 12oz cans with the 16oz. lower chuck adapter. With the 8oz. sleek can lower chuck adapter, the Mk16 is capable of seaming 8oz cans.