By default, products apply weights, dimensions and other settings to incoming orders when they are matched to order items. If a product is marked as inactive, the defaults for the product will not apply. This is useful for products that may not require this functionality.
Inactive products are essentially ignored in ShipStation.
To make a product inactive simply select the order, and then select the Deactivate button in your action bar.
Additionally, you can select the product and uncheck the "Active" box in the top right hand corner of the product details page.
To find inactive products, check the "Show Inactive Products" checkbox in the top right corner of the products page, directly above the columns.