Instruct: Classify a given review as either positive or negative.
Query: Poorly constructed, Not good with large breeds

I purchased two of these collars. I have a couple of labradors each about a yr old, the collar stopped them from barking right away, however they were curious about the others collar and easily popped the top casing off of these with one bite. When I returned from a 15 min. trip to the store I found both devices were in pieces.What a waste of money............ I have an older rechargable collar from Inotek that was bulkier but very sturdy have used it for over 3 yrs wish I could find another one of those.