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

Vertical Banner
paid action
This format can fit into small spaces. This size doesn't tend to perform as well as others due to its small size and limited supply of available display ads. Suitable for text ads and display ads.

Requirements
You need this to get it done:

Vertical Banner
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: 120 x 240 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