I haven't seen the concave ones, but my buddy had a yellow E 40 and we were disappointed we couldn't crush it or grind it. He got a finger nail clipper and clipped the pills into as many tiny littles pieces as he could and then we snorted it. It's a tedious process, but we were high out of our damn minds. I'm certain that if you took the thing to a ped-egg you could grind it into fine enough pieces to snort also, we just didn't have one at the time.