I bought this at a good price range and found this is really very effective, this protect us by keeping mosquitoes away from room this is why I say buy this if you want to sleep. one bottle works around 30 days which is cheap, very easy to use, just plug in and see mosquitoes moving away from your room. I tried many liquid but none of them worked as good as this worked. I have been using this for many years and still using this because quality is not changed. This is a must by product.