Our Jack Russel mix gives up on these once the outer layer has been nibbled off. His jaws are not too strong so he doesn't fancy anything rawhide-based. However I've seen both a Yorkshire and another JRT getting busy with these - they have very different tempers, the Yorkie is rather quiet but loves chewing these to bits (with great patience) while the other Jack Russell is usually extremely hyper but sits down with these and it keeps him busy for quite some time - his jaws are much stronger.