RF Adapter RP-SMA Jack to SMA Plug straight-long version

Some WiFi antennas and cables are designed for RP-SMA (reverse polarity SMA) and cannot be connected to a standard SMA plug. RP-SMA is a variation of the SMA connector specification which reverses the gender of the interface. The reason for that was a decision made by FCC in order to prevent end-users from manipulating certified WiFi devices at home, using other available SMA antennas. That lead to SMA and RP-SMA devices not being able to connect without an adapter, check Wikipedia for more details.