Any of the Samsung or Sandisk MicroSD cards will work just fine. However, I would not recommend using anything above a 128GB because the S5 Active really can't take advantage of the higher capacities with it's capabilities and cannot read/write the cards as fast as the newer phones. Unless you're shooting a ton of 4K video or you use the phone as a portable media player for movies/music, you really don't need anything beyond a 32GB card.