Farnam® 3002431 Sweat-Resistant Fly Spray for Horses, 32 OzProtects Against Biting and Nuisance Flies, Gnats, Mosquitoes, Deer Ticks and Lice. An effective fly spray that won't sweat off! The only fly spray with RepeLock formulation. RepeLock formulation is an exclusive conditioner that binds to the hair shaft, locking in the fly repellency of Endure fly spray. This unique formula stays active even when your horse sweats or in wet conditions. Size: 32 Oz Stays active and keeps working, even in wet conditions