Celebration Spot-On New, more effective, gentler formula kills and repels flies, mosquitoes, gnats, and ticks on horses for up to two weeks. The most complete protection available for horses. Water- and perspiration-resistant. Protects horses both day and night (when gnats and mosquitoes feed most often). Features: Water and perspiration resistant Easy-to-use, no-spill applicator with resealable cap Can be used with any Permethrin-based fly spray for horses Item Specifications: Size: Each box provides up to six weeks of protection.