The bike is a Giant Cypress with a 22.2mm Zoom adjustable quill. Hence the Nashbar threadless stem adaptor, which fits beautifully. Its lower section is 22.2 and the upper few inches is 28.6.
I was under the impression from the Nashbar Web site that the adaptor was intended to let bikes with 22.2mm threaded steerers use the newer 28.6 stems.
Although truth be told, Nashbar does not specify that it's intended for 28.6 stems in its description--they just say it will let you take advantage of "the great variety of new stems," or something like that.