There are two types of banners in Appodeal SDK: Adaptive and Standard banners (320x50, or 728x90 for tablets).
Adaptive banners are enabled by default.
The adaptive banner occupies the entire width of the screen, the height is selected dynamically for each device to maintain the ratio. If an ad network cannot scale the banner content without maintaining the aspect ratio, then the standard 320x50 size can be used. The ad networks, which don't support adaptive banners, will show standard banners.
Note: Adaptive banners will always return a constant size for a given device and width.
To disable Adaptive banners, you can invoke this method before SDK initialization (Native Android example):
Appodeal.setSmartBanners(false);
In this case, the banner size for both phones and tablets is 320x50.
To enable 728x90 banners for tablets, you can invoke this method (Native Android example):
Appodeal.set728x90Banners(true);