Instruct: Classify the given review into positive or negative sentiment.
Query: really bad

i always buy this brand for cooling systems, until now it was perfect, but i bought this fan and it is incredible how useless it is, it didn't affect the temperature in the case and if you put your hand on the vent in the back of the case you can figure out why doesn't help, it's to slow. Don't buy it you'll regret it like i did.