Schutzhund has specific dumbell requirements for each level of title. These
regulations are based on weight.
A wooden dumbell proportionate to the dog's size is nice for training. In order to extend it's useful life and also to provide some grip and give/softness to the mouthpiece of the dumbell, a wrap of some kind can be used. My favorite is vet-wrap because it is easy to apply as it sticks to itself and can be wrapped several times to provide good thickness and give. When it gets really slimy, just cut it off and apply a new length.