Small FYI for the folks who are saying that the lack of MicroSD is a deal-breaker.
Sandisk, (and others), do USB "duo" flash drives with normal USB and MicroUSB connectors. So if your phone supports OTG (and I'm willing to bet that the S6 does) then you're "good to go". Downside is that it looks pretty untidy, but it's also a little easier to load from a PC than a MicroSD card.
Typical unit is SanDisk Ultra 64 GB Dual USB Drive (SDDD-064G-G46) which is actually cheaper than an equivalent MicroSD card (the USB drive is £20.14, the card is £24.70). And if that's a little on the expensive side, then 7dayshop have an own-brand unit for £15.99.