Action Details
Requirements and how-to articles for Google Ads's action:

paid action
Third most popular size in Poland. Can be used as an alternative to the 'double billboard'. Currently only available in Poland. Suitable for text ads and display ads.

Requirements
You need this to get it done:

Triple Billboard
You can create a responsive display ad, or upload a display ad. You can also choose to copy existing ads.
You can upload image ads as .gif, .jpg and .png
You can upload AMPHTML ads as a .zip containing 1 HTML document and up to 39 media assets.
Maximum file size: 150KB
Dimensions: 750 x 300 pixels
Requirements missing or found errors? Report

How-To Articles
A list of useful links for you:

0
Google AdSense Help - Guide to Ad Sizes
List of different ad sizes and how well each one performs.
Official
Link missing here or found errors? Improve How-Tos