This split pane component is dynamic: when re-sizing the browser window, the width will adjust.

Set last component size to 150px

This split pane component is fixed: when re-sizing the browser window, it will keep the same width.

You can, however, re-size this component by dragging the divider, and it will adjust if the left component reaches it's min-width (10em in this example).

Set first component size to 300px