The 300×250 ad is the IAB medium rectangle that is available for both phones and tablets. While all AdMob/AdSense policies and the information on banner ad guidance still apply, we want to share specific guidance regarding this ad size due to its unique size and shape.
EXOCLICK 300X250 BANNER CPM
Banner
Ads that get attention
Classic display banners in many sizes: 160×600, 300×250, 728×90 and 900×250