OFF!® Clip-On™ Mosquito Repellent Refills are sold separately for use with OFF!® Clip-On™ Mosquito Repellent fan units. Each box of refills contains two repellent disks. If you move, allow a few minutes for protection to rebuild. Each repellent disk provides up to 12 hours of head-to-toe mosquito protection and will work with previous and new designs of the OFF!® Clip-On™ Mosquito Repellent unit. Use each refill within 14 days of opening.