For native-style programmatic ads, it’s best to use banner sizes that blend naturally with the content on the site. Common sizes like 300x250, 728x90, and 320x100 tend to perform well. These sizes are widely supported and often placed within or near content, which helps them look more like part of the page instead of a regular ad. Native banners usually rely more on layout and placement than just size, so making sure your image, headline, and call-to-action match the look and feel of the site is also important. Some platforms even offer responsive native formats that adjust size based on the screen or placement. What sizes have worked best for you so far?