Ultrashield in the black bottle is my favorite, but it fades their coats like crazy.
Ecovet gives me an instant migraine. I had to ban even the boarders from using it, unfortunately (it’s my barn and I want to be able to feed everyone’s horses without being disabled for the rest of the day!). Fortunately I have a great group and they understand.
I honestly haven’t found anything that works for long, so I have an array of fly and mosquito sheets for my herd. They work the best. ShooFly leggings are awesome but don’t last long. I am trying some knockoffs from China that I got for like $5 and then some really expensive ones from another brand this year, trying to find something that will last all year. My horses are out 24/7 so a year is about all I expect from any fly gear.