We began using Fly Predators in 2006 when we lived in VT. We had 5-7 horses at any one time, with a total pasture area of about 10-acres. The results were great. Following their directions on how to order the proper quantity is key, and the manure management tips they provide also helps. Since moving here to CT about 10-years ago, the results have been even better. I definitely recommend over-ordering - meaning if you have 2 horses and 3-acres, order the amount listed for 3-4 horses and 5-acres - that kind of thing. Especially in the first few months of using the product. Apply the Fly Predators as directed, don't skimp, and stick with their program. You'll have great results. Our horses never have to wear "fly masks". Our neighbors are very close (their deck is only 100-feet from our barn) and they always comment on how they never have any flies. You'll still likely need to use a fly spray during the heart of fly season, but this product always performs. We've tried others a few times in the past, but Spalding Labs is BY FAR the best and best value for the money.