The 300×600 Ad Unit provides Publishers High CPM rates
Equivalent to a full-page ad in a newspaper, the 300×600 ad unit, or half-page ad unit provides a large area for advertisers to display their message. As a result, the 300×600 ad space commands a higher CPM rate than other standard ad units. Typically, very few sites select this placement causing a higher demand from advertisers. This ad unit is included with the 300×250 as a dynamic tag; the tag will show the size of the highest-CPM impression that is available. This method allows you the flexibility of a standard or high-visibility unit on your site while maximizing your revenue. 300×600 ad unit placements are typically placed top left or middle left alongside content.