There's a difference between fair use and taking unfair advantage of a brand owner'S trade mark. Your example would be likely to fall within the nominative use bracket as you're using the term to describe an attribute of the product. On the other hand, using a third party's trade mark with a clear intention of free-riding on their goodwill will be considered to take unfair advantage of that goodwill and be an infringement of trade mark law. Rolex Tractors would be an unlikely example.