X-10 is both a company and a standard protocol. There are various branches of X-10, including X-10 Pro, X-10 Retail and x10.com. These branches often have the same items, but by different part numbers (or names). And some parts are available only through one branch. Pricing varies greatly between branches and over time as the branches compete against one another for wholesale and retail business. They are, to say the least, unique.
