Answers for "stretch flex"

flexbox stretch

.flex-container {
	display: flex;
	align-items: stretch;
}

css flexbox syntax

Display: flex 
Flex-direction: row | row-reverse | column | column-reverse
align-self: flex-start | flex-end | center | baseline | stretch
justify-content: start |  center | space-between | space-around | space-evenly