Compact and lightweight easy to carry for indoor and outdoor use USB powered,plug and play.They can be powered by any usb outputs Like Digital device,power bank,AC chargers,car chargers and more.easy and convenient.Adopt the heating element of the PTCR with constant temperature for stable performance.Standard refill tablets they can be used,you can buy it at your local store,and the package include 2 PCS Replacement refills for free.Best suitable for outdoor using,like fishing,driving a car,camping,Hiking and more,and just need a power bank to power it