CSS FlexBox Model: Difference between flex and box-flex?

Using the css flex box model there are many different properties.

What is the difference between the following properties?

-webkit-flex: 1;
-moz-flex: 1;
-ms-box-flex: 1;
box-flex: 1;

and

-webkit-flex: 1;
-moz-box-flex: 1;
flex: 1;

How do I combine the old and the new syntax?