SEA&SEA’s zoom gear for the above is only compatible with the redesigned ‘Contemporary’ lens (indicated by a C label).

The SIGMA 17-70mm F2.8-4 DC Macro OS HSM lens was redesigned in 2013.
SEA&SEA’s zoom gear for the lens shown in the system charts (#31169) cannot be used with the older version of the lens.
The new type ‘Contemporary’ lens has a C label on the barrel.