dog collars

Question
i have two year old labs.  they have a dog run that they share.  we had the easy release fabric collars that they chewed off of each other.  i have gotten them choke chains so that i can keep id tags on them but don't like the choke chains.  do you have any suggestions about collars that they can't chew off?

Answer
This is a tough question.  It is best not to allow dogs unsupervised play with any collar, and the choke collars are worse than others.  You might try a heavy, studded leather collar.  You could have them chipped, and leave them in the run without a collar.  There is a conflict between the safety of having a collar and ID, and the danger of any collar strangling the dog.