The surface is just sticky enough to hold the sim card in place without getting it all gunky.

The tacky silicon surface is great at holding things on

The SIMS and SIM tool stick to the tacky surface perfectly.

The sticky surface of the tray is perfect for keeping the SIMs in place

The sticky surface of the tray is perfect for keeping the SIMs in place

As such, it is possible something could get bent or deformed if you put it in your back pocket and sit on a hard surface.