Use for hold 18650 battery in center of LED flashlight that powered by 18650/ 3AAA batteries.
Please check the sleeves Dia what you need before you choose the sleeves, the plastic sleeve does not fit for Flashlights that use 26650 /18650 batteries flashlight (such as 878 flashlight), which need a bigger Dia sleeves for this kind of type flashlight.
If you only put a 18650 battery in the flashlight, it will be flopped freely in it. These battery converter are very useful to increase the diameter of 18650 batteries to better fit flashlights. Put one of these sleeves in it and it minimizes the flopping.
This sleeve prevents the inner wall of the flashlight from colliding with the battery to protect the battery.