Why slot 1?
In dual slot smartphones, you have to put Surfroam SIM into slot 1.
It is guaranteed that SIM card will be activated correctly and registered in a network as fast as possible.
Also, it helps to make set up process simple and handy.
Slot 2 supports "simple SIM's," local SIM's and SD cards, in many cases depending on manufacturer device slot 2 do not support new smart SIM technologies.
Slot 1 supports all types of SIM's, including "smart" SIM's with more memory and functions.
Your local SIM will work fine in slot 2 during your next travel. You may choose in settings which slot serves as data only channel and the second one is for calls and messages.
Stay connected with Surfroam and have a nice travel!