I can\'t comment on the sizes as we don\'t use them, but the spiral ones I have seen were plastic, and i believe that was their purpose to stretch as the bird grew??
Anyhow before investing much $$ you might want to concider a more perminate and unique identification.
Here in NY they will still accept our bands as long as the are \"perminant\" and uniquely numberd.
(we use numbers wing bands with the farm name on the back, others just use numberd ones and still others leg bands, but the kind that seal on so as to not be easily removed)
with all the identification and farm registery etc it might be wise to al east give them a run for their money.
the state vet feels that as long as we can claim and prove that we do identify each individual bird uniquely, then we will be expemt form the nasis registry, (but that too is just her opinion), I think eventually we are all gonna get hit with it!