mspace1

W3C sample	WIRIS
	$x M x$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mi>x</mi>
    <mstyle mathbackground="#000099">
      <mspace height="1ex" width="1ex"/>
    </mstyle>
    <mi>M</mi>
    <mstyle mathbackground="#000099">
      <mspace height="1ex" depth="1em" width="1ex"/>
    </mstyle>
    <mi>x</mi>
    <mstyle mathbackground="#000099">
      <mspace depth="2mm" width=".2in"/>
    </mstyle>
  </mrow>
</math>

Author: Robert Miner and Jeff Schaefer, Geometry Technologies