The adhesive surface is a silicone adhesive surface, from which the device can be repeatedly removed and re-stuck. The surface can be washed off with water.
Since the mobile phone is waterproof, Sony has done well to issue no leather cover, as this would not nunmal waterproof. only the plastic window on the front feels very billg and is dirt-sensitive.
All in all, fits the envelope but precisely and is worth the money.