Product Size

Each product can have the size defined: Length, Width and Height. The size fields appear inside the product details box on product add/edit screen:

Product Details Box SKU

Set Catalog Size Unit

In order to change the size unit go to the Catalog Settings > Attributes. The size unit option is available below the attributes table:

Size Weight Settings

You can also disable the size feature completely. In order to achieve it go to the Catalog Settings > Attributes and switch the Size Unit option to Disable Size.

Disable Size Weight Settings