The easiest way is to select the extrusion (the tube), right click to bring up Properties, then, if not already chosen, choose Simple Extrude Shape and set the height (which is the Z dimension) to whatever you want.
By the way, instead of creating a tube by extruding a circle and and then subtracting another extruded circle from it , try drawing two concentric circles and boolean subtracting the inner one from the outer, then extruding resulting torus.
Another way is to draw the two concentric circles as above, then Simple Extrude and then right click and choose Use Compound Profile, then, with the shift key depressed, select the circles, release the shift key, and the extrude will work as before but the result will be a tube.