Instruct: Classify Amazon reviews into positive or negative sentiment
Query: unsatisfactory model

I have previously purchased (several years ago) a Thermo Kitty mat that looks the same as this one. The electrical unit in the first one I first purchased is approximately the length of the fleecy cover. I was unpleasantly surprized to discover that the heating unit in the newly purchased mat is only a small square, leaving approximately 2/3rds of the total mat surface unheated. I returned it immediately and purchased a competing brand that heats the entire bed surface (or close to it). My two arthritic and very elderly cats (17 and 18 years old) love their heated beds and stretch out full-length. I don't think they would be as comfortable if they had to curl up tight to get the benefit of the heated area.