Hello,
The difference between RUTX12 and RUTX11 is that they have different numbers of mobile modules. The RUTX12 has two mobile modules, so it can support two SIM cards simultaneously. RUTX11, meanwhile, has a one module and only one SIM works at a time. Although the RUTX11 has two SIM slots, but only one SIM works, the other slot is used as a backup.
Best regards.