According to the brochure they are 4 dBi (with u.FL connector).
https://i.mt.lv/cdn/rb_files/wAP_ac_LTE ... 101931.pdf
Looking at the Quick Quide it looks like you can use your own antennas.
https://i.mt.lv/cdn/rb_files/1560237514 ... series.pdf
MiniPCIe slot usage
The device is equipped with a miniPCIe slot (a kit with preinstalled modem also available) to be used with a 3G/4G/
LTE modem. A SIM slot is provided for use together with a miniPCIe modem. SIM slot is not usable separately.
To install the miniPCIe module, remove both screws below the power jack and slide out the wAP PCB board. Insert
the miniPCIe modem, and secure it with two Philips screws which are already in place.
Attach the grey uFL connector to the MAIN antenna connector of the modem, attach the black cable to the other (or
AUX) connector. It is possible to use external antennas for the modem, two SMA mounting holes are provided next
to the reset button, or if you prefer to attach antennas to the case directly, SMA antennas can be mounted on the
bottom of the case if you remove the two plastic hole covers first.