The Insect repellent collar is a very easy and effective way to give your horse constant and total protection from flying insects. The insect repellent collar for horses contains a blend of natural ingredients to protect the horse against most parasites such as flies, mosquitoes, horseflies and midges. This soft and easy to wear collar for horses is effective for 3 to 5 weeks depending on the climatic conditions. Once the active ingredient reaches the surface of the collar it then migrates across the horse to give total coverage. Fully adjustable, can be easily cut to fit. We use these on our horses: I use them on my 4, and I find them to be about 80-90% effective- the same as the expensive fly repellents- and they last around 4 weeks on mine in rain and shine (mostly rain!). My horses have them on 24/7 with no rubs or problems and I ride and do everything as normal with them on with no bother. They are all natural ingredients and none of mine (including the sensetive one) have had any problem with the ingredients and it is so much easier than having to spray some very unhappy horses twice a day!