Purely aesthetic product features can be protected as trademarks if they are source-identifying and non-functional. Product or packaging features that are not purely utilitarian, but are aesthetically pleasing and are an important ingredient in the commercial success of a product are not eligible for trade dress or trademark protection. When an aesthetic product feature serves a significant non-trademark function, the feature might not be protected as a trademark. This is because it would stifle legitimate competition to do so. Significant non-trademark function of an aesthetic product can be determined by the use or purpose of the article, or the cost or quality of the article.