I know the official specs say 32GB only, and I know that people here are using 64GB cards. So, has anyone used a 128GB card? Now that I have my OTG cable, I'm going to move past the 32GB card I currently have. If a 128GB card works, I may get one.
See above link Lumia with WP 8.1 support 128 Gb SD.
I am not sure which phone you have but in the past these cards where not present so that's why it is probably not in the phone spec
But now the bad news. Windows phone do not support OTG.
I am using a Lumia 830 with a 128 GB SDXC card. Currently using a bit more than 80 GB of that space. Works just like any other SD card. Nothing out of the ordinary to report.