Futurelooks posted a review on the D-Link ANT24-0230 Xtreme N 2.4GHz Antenna

The D-Link ANT24-0230 is an external antenna that replaces the stubbies that come stock with your DIR-655 (or DIR-660 & DIR-625) router. It is also compatible with the DWA-552, DWA-556 & DWA-542 desktop adapters. The ANT24-0230 allows you to extend your antenna away from the router or desktop adapter, providing you with more flexible placement options. This should, in theory, allow you to get better signal quality by
allowing you to pick a better spot for your antennas.

D-Link ANT24-0230 Xtreme N 2.4GHz Antenna Review