If the element is not a flexible item, the flex-basis property has no effect.
Note: If the element is not a flexible item, the flex-basis property has no effect.
flex-basis
Supported Browsers:
Set the initial length of the flex items to 50 pixels, with an exception; set the initial length of the second flex item to 100 pixels:
Note: Internet Explorer 10 and earlier versions do not support the flex-basis property.