My son has a VERY large dog with jaws like a lion and he could rip anything up no matter that some were said to be indestructable, he could destroy it. Once when he was here he found my dogs little Nylabone Dental Dinosaurs and started to chew it. Couldn't destroy it. He loved that little Dinosaurs and chewed it each day. I let him take it home and since then I have always gotten him one for his birthday and for Xmas. His favorite toy, and he has never been able to chew them up. I get them at
http://www.petedge.com the number to them is TF22101 It's the durable one. They have a flexible one too, but it's too soft.