Google made available product extensions to U.K. advertisers, that allow of using existing Google Merchant Center account to highlight products directly in search ads. When AdWords text ad appears, and GMC account contains products relevant to searcher's query, product extensions show images, titles, and prices of your products in a plusbox under your ad.
"With product extensions you can show users products from your site most relevant to their query. You're charged same CPC whether a user clicks on main text ad or any offers within product extensions plusbox; however, you won't be charged if a user simply expands plusbox without clicking through to your site," explains Google.
To get started: First, log in to GMC, add your AdWords customer ID to your account. Then, log into AdWords, select campaign and navigate to Ad Extensions tab. To add product extensions to an existing campaign, click "New Extension" button. No need to create new campaigns or ad groups, update your keywords or change your ad text.