It is very easy for a Yorkie's trachea to collapse with any pressure applied to it. Using a leash with a collar will apply such a pressure. Their necks are so tiny anyway - they just don't need antyhing that can possibly hurt them. Please always use a harness with a leash. Lots of harness vets products available from members.
P.S. Welcome to YT. You can search under Harness or Collar and find lots of information also...
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