I've used and abused a variety of gaiters by other manufacturers (i.e. Kenetrek, Outdoor Research...) and the Sitka ones are vastly superior.
They are very durable, fit extremely well, never come loose (read: strong zipper + velcro + snaps), the heel strap design is very well thought-out, and if you're wearing expensive boots, these gaiters will protect your investment.
best gaiters I've ever used 
