No - extension tubes have no glass in them and are a lot cheaper - they simply space the lens away from the camera so the focus distance is reduced. It's good for macro but you can no longer focus to infinity.
Amazon.co.uk: Kenko Ext Tubes Canon EOS Mount: Electronics & Photo
You can get them a lot cheaper than that - I paid about £70 for the Jessops auto tubes which are fine, and someone like B&H should have some.