Card

The default container for any self-contained block of content or settings.

CardAction lives inside CardHeader and spans both title rows — never float a button yourself.
Use CardFrame when the title belongs to the plinth and the content is a distinct inner slab.
Cards side by side fill the row height, so put the footer in CardFooter and the stacks align.
No coloured left border, no gradient — Reckon cards are white on white, separated by the hairline alone.