The "One size fits all" is misleading and only refers to the arm size. My Samsung S7 Edge fits in tight. That's a 5.5" screen phone. This piece will not be suitable for any phone that's larger. In terms of functionality, it seems quite convenient.
Not worth its price as it doesn't protect phone from sweat
I bought it for my running sessions and from the start I felt it loose around my arm but if I pull it tighter, it digs into my arm, quite uncomfortable. Quite expensive at £6.95