Targus ACP60 - Manual (Page 6)

The spacer simply snaps on to the existing ExpressCard and is
inserted with the card connector into a 54mm ExpressCard slot.
A spacer is available for the ExpressCard to ensure the proper fitting of
the 34mm ExpressCard into a 54mm slot. This spacer has no function-
ality other than to prevent any movement of the card once it is inserted
into the 54mm slot. The spacer is not needed if you have a 34mm slot
on your notebook. (See the diagram below as to the two different slots
that are currently shipping in today's notebooks)
Using the Spacer Connector
Carefully align the spacer with the ExpressCard and join the two
pieces together by locking the clip in place.
Please make sure that the clip is firmly secured and no gap is in
between the two items. As shown in the diagrams above.
Targus ExpressCard Notebook Docking Station with Digital Video and Audio
5