I have attached the white one to my crystal clear Spigen case, and it adhered well. I've used it heavily for two days, with much in and out of pocket action. The the card holder is showing no signs of losing its adhesion. I keep three cards in the holder and think that is probably the limit. Two is a better fit. One card stays in the pocket, but after having three cards in the holder for two days, one card alone seems a tiny bit loose.