Mine chew up nyla bones, too, so no more of those. Now I give them those smoked rib bones once in a while and they chew on those for months. My strongest chewer really liked cow hooves, but you can't always find them.. . but sometimes Walmart carries them. If you are in a small town, check the farm supply stores - they often have them. I like natural things because they mostly gnaw on them, they don't bite them into pieces, so they last and last.