One of lesser known middle men in the industry - HookLogic - has captured $15.5 million to expand its advertising network and technology.
The Series C injection comes via new investors Fung Capital and Mousse Partners, with existing backers Bain Capital and Intel Capital also participating.
Previous rounds came in 2013 (Series B: $14 million) and 2011 (Series A: $9.5 million) for the 11-year-old company.
US-based HookLogic calls itself a "retail search exchange" and works by handling placement for suppliers on "premium" channels on intermediaries.
Two of its services are for general retail products and a new push into automotive sales - but it has a particular focus on travel services.
It works with likes of Expedia, Priceline, Hotwire, Hotels.com and Travelocity, making use of high placement positions on their respective search results.
The capital raise will be used to expand the company's staff head count and enter new markets overseas.