Review on Tupavco TP511 WiFi Panel Antenna 2.4GHz (20DBi) Outdoor Directional (2400-2483 📶 MHz) Wireless Network Signal (Pole Mast Mount) Weatherproof High-Gain Long Range (N-Female Connector) by Curtis Domus

This is a 16 element PCB patch antenna. Better quality than I expected but not 20dBi. Theoretically, 16 elements result in 18 dBi. Considering the solder joints aren't the best, I'd say this antenna really works at 17-18 dBi. The best for the money I've seen. I've searched for them and haven't found a Declaration of Conformity (FCC) so I would guess they are trying to stay clear of the FCC by increasing the max power from 400mW to 316mW or (power plus 18dBi antenna) from 44 dBm down to 43 dBm (EIRP). I'll run 400mW through them :) If you're going to use this antenna outdoors, I'd suggest using some silicon around the entire trailing edge, except for the bottom hole (whatever that is for your polarization application).