Below is an example of an extended sitelink.
Why would we advise people to use these as appose to the normal sitelinks. Well which of the attached would you rather click on? the small normal ad or the nice new big ad? Simply – the new sitelinks take up a lot more room on the page increasing the chance of a click, thus increasing CTR and reducing CPC
However more importantly than the “taking up more shelf space” and effectively having 5 ads (or in some cases 3 ads when only 2 extended sitelinks are shown) are the actual results of these sitelinks. Having tested this on a variation of clients we have noticed the CTR improving by as much as 100% in some instances. On average however it is more like 70% by which the CTR improves.
The how to guide is provided by Adwords right here: http://adwords.blogspot.co.uk/2013/06/give-your-sitelinks-additional-detail.html
For more advice on how to best implement this or any other PPC expert advice, do not hesitate to get in touch with the Circusmedia team.