I found this on the web:
"The VU+ Duo2 is equipped with 2 tuner slots. So you have the choice of which tuners you want to install in these. These are the current possible tuner config options
DVB-S2 + DVB-S2
DVB-S2 + DVB-C/T
DVB-S2 Dual + DVB-C/T
DVB-S2 Dual + DVB-S2 Dual
DVB-C/T + DVB-C/T
So you can have a maximum of 4 DVB-S2 tuners by using 2 DVB-S2 dual tuner modules."
If your tuner has two sockets both marked LNB IN, it's a dual tuner. If one socket is marked LNB (or RF) IN and the other is LOOP OUT, it's a single tuner.
It depends on what you ordered !!!