Most models come in two sizes, 38 millimeters and 42 millimeters, as measured by the height of the watch face. The larger one costs $50 more in most cases. For a few of the bands, only one size is available.
There are three lines to choose from:
— The cheapest is a "Sport" version with an aluminum case. You can get it with a silver case and choose a white, blue, green or pink band made of synthetic rubber. Or get a grey case with a black band. The smaller version costs $349, and the large one is $399. That's 10 configurations — five bands, each in two sizes.
— The regular version has a stainless steel case. The cheapest has the same band as the Sport version. You choose white or black and pay $549 for the smaller model and $599 for large. Fancier bands are available — three different leather bands, a link bracelet or a Milanese loop. Prices go as high as $1,099 for a large watch with a stainless steel link bracelet. There are 20 official configurations, but once you factor in some leather bands coming in two or three sizes, you have 32 options to choose from.
— Edition is the luxury line with cases made of 18-karat gold alloy. It's $10,000 for a small version with the white or black band that comes with Sport models. The large one costs $12,000. You can get a leather band for $15,000 or $17,000, depending on the size. There are officially eight luxury configurations, or 12 if you count band sizes as choices.
Apple is also selling bands separately for those who like to swap designs. Prices range from $49 for the basic sport band to $449 for a link bracelet.
To help you choose, Apple has plenty of videos on its website and Apple Store and Apple Watch apps. The Apple Store app also has sizing guides, images of the watch cases in actual size and animation of buckles and clasps, which you can open and close by pinching in and out.