I bought it here http://northwindcatalog.com/product-page-new/martingale-collar-master/

Whippets have long necks and their heads aren't much bigger than the base of the neck, so a standard collar is either too tight or the dog can slip out easily. The Martingale type is a semi-choke, so it tightens up if the dog pulls. I like the wide ones because by spreading pressure it's kinder to the dog. (My dog is pretty well trained on and off leash but he's still a dog and has moments when he forgets his training.)

I bought a new one recently that has this stripe of nautical signal flags sewn on, and a matching leash too. I also use a Wichard mini-snap shackle to make it easy to move his tags between collars.