<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1" id="svg2816" height="64px" width="64px">
  <g  id="pale-red" style="fill:none;stroke:#280000;stroke-width:8;" >
     <path d="M 16,48 48,16"  />
     <circle r="26" cy="32" cx="32" />
  </g>    
  <g id="red" style="fill:none;stroke:#cc0000;stroke-width:4;">    
    <circle r="26" cy="32" cx="32" />
    <path  d="M 14,50 50,14" />
  </g>
  <g id="dark" style="fill:none;stroke:#ef2929;stroke-width:1.99999988;">
    <circle  r="27" cy="32"  cx="32" />
    <path d="M 12,50 50,12" />
  </g>
</svg>

Update icon for Sketcher Constraint Block
Update icon for Sketcher Constraint Block

The existing icon for the sketcher constraint for "constraint block" is easily confused with the icon for the diameter constraint. A small modification to add a 2nd cross bar will visually distinguish it.