California Code, Revenue and Taxation Code - RTC § 6379.5

There are exempted from the taxes imposed by this part the gross receipts from the sale of, and the storage, use, or other consumption in this state of catalogs, letters, circulars, brochures, and pamphlets consisting substantially of printed sales messages for goods and services printed to the special order of the purchaser and mailed or delivered by the seller, the seller's agent, or a mailing house, acting as the agent for the purchaser, through the United States Postal Service or by common carrier to any other person at no cost to that person who becomes the owner thereof.