Step 1		Begin with a UV Sphere
Step 2		Scale along the Z axis by two
Step 3		Tab into edit mode
Step 4		Shift Z into wireframe mode
Step 5		While holding shift, select the top and bottom sections
Step 6		Press X to delete the sections
Step 7		Exit wireframe mode by pressing Shift Z
Step 8		On the right, add modifier>subdivision surface
Step 9		Here is the smoothed result
Step 10		On the right, increase the viewport levels from 1 to 3
Step 11		Significantly smoother
Step 12		Tab into edit mode
Step 13		Select all
Step 14		Checker deselect
Step 15		Here is the result of checker deselect. holding shift+alt click the top and bottom rings
Step 16		Here is the result of selecting the top and bottom rings. press CTRL+i to invert the selection
Step 17		Here is the result of inverting the selection. Press s than, shift z to confine against the z axis
Step 18		You can drag the mouse or press 0.1 to scale to a preset value.
https://www.youtube.com/watch?v=NtJiDY9tzek