Hi, I've not come across that product or tried it, but certainly the flies seem to be out in force this year!
I think unfortunately you need to take a holistic approach to dealing with these things. Yes certainly a good
horse fly sheet is important, but also things like try moving your horse to another area of the field, particularly at certain times of the day can help.
I've also heard that other supplements to the horse's feed such as garlic or brewer's yeast can also put off the midges! They make your horse's blood carry a higher ph acidity - doesn't harm the horse but tastes horrible to flies!
Good luck and let us know how you get on!
Claire