Easy to use - takes a while for the flys to find it but it does as advertised when they do.
Takes more than one of them to make much of a difference. I installed four of them under the car port where the cats are fed and have seen good results.
I placed this with a Walmart variety,(Rescue)$4.95 the Walmart holds about half less, (about 20K)but is more (actually a lot) effective; starts collecting immediately, the other takes a day or three). I live in a subdivision with lots of dogs, thus flies.