Don't waste your money on an ebay antenna, mate. If it's a wifi antenna you want that actually works buy one from the C.Crane company. We use two Crane antenna's when we travel (one on the road & one at home) and find them to do a great job of signal capture.
C. Crane Company - WiFi Antennas - Toll Free (800) 522-8863
Tip: check out their "Orphans" (link in top bar of page) to find any product they sell at a discount since all are certified returns.
Info to help you decide:
http://www.countrymilewifi.com/