Dimensions for products may be required for some merchants to show the height, depth and width.
Activate the Product Dimensions Enhancement
Head to the first product you would like to add dimensions to and scroll down to the "Dimensions" panel.
Select the measurement units you would like to use from the list under 'Class' and add the Height, Width and Depth/Length as needed.
Click Save and head to the Product Page on your Shop Front and check it's all correct.