After 2.5 months crumbles

Actually, a product of what the device is slim, the slippery 830 provides a good grip.
But it is now crumbling after 2.5 months and has sharp edges. And it happened when pulling out of his pocket after times the smaller bridges were broken at the keys in advance.
Too bad I had with the predecessor (Lumia 925) a cup was the blunt of the surface and held more than 1 year.
So the really cheap price is still high in proportion.