It is best held directly on the smartphone. It still works with a very thin case, but is no longer as stable. I use it together with the Kaiser camera grip, the Ulanzi smartphone holder, a Samsung USB-C stick 512 GB and a DJI Mic Mini. All together on a tripod, with an LED light if required. This gives me a top video system that records directly to a USB stick (with the Blackmagic Camera and Final Cut Camera apps). A top rig!