Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Do not use as the primary collar, But Great for lighting

I bought two in large. One for a 98 pound German Shepherd and another for a 80 pound Ridge-Back.The light is provided by a flexible clear plastic cable looking gizmo that makes the entire collar appear to glow. It is not super bright, but they really stand out during a dark evening... It makes your dog easy to spot when they run off into the woods and it helps cars to see us during our evening walks. HOWEVER, they do not hold the size adjustment. If you try using it as the only collar, any jerking against the leash will open up the collar and the dog will slip right out. Plus the section that looks like it might also be reflective is not...