Rugged and versatile, ripstop is a specially engineered nylon material coated with a layer of polyurethane on one side for superior water repellency. The name "ripstop" refers to the fabric's small, tight windowpane weave, which makes it extremely strong yet surprisingly soft and lightweight.
In addition, because it is reinforced with a double thread of nylon cord every quarter inch, the material is resistant to the expansion of small rips. You can use any terry-cloth towel for this project; Martha uses an oversize beach towel measuring 60 by 72 inches, which requires approximately 2 yards of the corresponding ripstop.