I have the iPhone 6s plus and the spigen neo hybrid case. It fits and still has a few mm of space. Buy it and if it doesn't fit, send it back ;)

I have an LG G4, which is 7.8 cm wide with the case and fits easily. It's a great holder, I'm very satisfied.

I only have about 3cm of free space on the edge of my phone where the holder is clamped. Is this enough or do I need more space?