Thanks, Looks like SK has three options for devices (eggs)
https://www.skroaming.com/modem/modem_rental.asp
CLR-1000KS, AMR510L, and SKL321RM
There's no info on the differences. It seems some may be bigger than the others. Perhaps (guessing) the bigger ones have a longer battery. They might also have a larger coverage area (One person in one room and another person on the other side of the house kind of thing)
Any one have any idea?