The E55 is ideal for the backyard, poolside, patio, camping and more. Enjoy 12 hours of continuous mosquito protection with the included scent-free refill. Stay protected even longer with a 40-hour refill (sold separately). Powered by a rechargeable lithium-ion battery, E55 provides 5.5 hours of continuous mosquito protection on a charge. USB charging cable included. Allow 15 minutes for full effect. Can charge while operating to extend run time. Repel mosquitoes without chemicals or sprays on your skin. No lotions or DEET to apply. No smoke, flames, or citronella. Not a messy trap or gimmicky sonic. Independently tested. EPA reviewed for safety & effectiveness.