Product review (5 stars): Antenna Specifications
This antenna set contains a 3-petal cloverleaf antenna and a 4-petal cloverleaf antenna.  The connector is RP-SMA (reverse polarity sma).  The antennas are listed as 18 dBi gain - but this is not correct.  They are about 2 dBi.  This is a misprint on the part of the manufacturer.

I measured the VSWR and efficiency of these antennas (which were both very good) and they are listed here antenna-theory.com/review/3drobotics-cloverleaf.php

For circularly polarized self install antennas, you're not going to do much better than these.