We bought this popular antenna after becoming suspicious of it’s fairly high directivity (13 dBi gain) on both WiFi bands in the small 5″x9″ size and modest price. It turns out that it comes close to meeting these claimed specifications. It is about 10 dBi in the 2.4 GHz band and 14.5 dBi in the 5.5 GHz band. All reasonable for under $40. It was silicone sealed and would have some outdoor weather protection.
The photo gallery below has the pertinent performance graphs, measured 3D gain patterns, test setup photos, and internal views.