I bought this based on the online reviews. I read the package on the way home and it said repells mosquitos and black flies. I thought wow I hope this works but really didnt believe the flies thing. Well, we got home and turned it on and there were at least 5 mosquitos at 2pm in the afternoon and about 15 flies around our porch. We went inside and came back out about 30 minutes later and there were no flies and no mosquitos it was great! It comes with one butane container and 3 cartriges. It says lasts 12 hours, I thought that meant per cartridge but it means all together. The only bad thing about it is that the refills are almost $9 and that lasts for 12 hours so it would cost you $9 a day at least to keep them off your porch. If you just use it for special occasions like hunting it would be fine but when its an everyday thing it can be expensive but I must say....well worth it!