This Design was inspired while using small E Cig and vape sticks. They always seem to roll away, fall over, get misplaced or just plain lost. With this holder not only do you have a better grip on your stick. You can stand it on a table, it is less likely to fall out of your pocket and you can clip it to your car visor. This will hold CuraLeaf vape sticks and mark 5 e-cigs or batteries with same diameter. Inside diameter of cap is .395" or 10mm. The front opening allows air in and lets you see the device light up while in use. If fit is to loose, add a small piece of tape around ecig body for desired snug fit.