How can I resize this object without distorting it in Illustrator?

How can I resize such items without changing the curvature at edges? You know, I don't want the half-circles at the extremes to become half-elipses.

thanks

Answer

Hold down the shift key while dragging a corner handle.

Or, the more accurate and flexible method is directly selecting all the vector point anchors for one side (2 corners) and dragging that over, then selecting the other half to drag another side in another direction to achieve the desired dimensions.

diagram to show how to resize by directly selecting anchor points

You can only do that with the "Direct Selection Tool" which is the second, white, "pointer" button in the Illustrator tools palette. It selects points of a shape instead of the whole shape.