An exertube consists of two handles joined by a peice of rubber tubbing. An exertube is not as versatile as free weights but it is very convenient for travelling or storage in the home. An exertube is sometimes called an x-tube or a resistance band, they are ideal for all fitness levels and are available in many different thicknesses.
A small disadvantage with the exertube is that the more difficult the exercise becomes the band is extended.
You can purchase a exertube from many, high street stores, sports shops and online.