Glas-Col's fabric heating mantles offer certain advantages not available with rigid aluminum-housed mantles. They conform easily to the shape of the reaction vessel and are available in shapes that would not be practical with an aluminum mantle. In addition, it is usually much easier to magnetically stir a reaction vessel through a fabric mantle compared to aluminum. And the price is usually lower than the corresponding aluminum mantle.
Of course, the outer canvas lining is not as durable or rugged, so it can be prone to staining, tearing, or absorbing chemicals that are splashed on the outside.