Weighing and measuring your products for Shopify Fulfillment Network
You aren't billed based on the weights that you enter in your Shopify admin. Instead, Shopify Fulfillment Network (SFN) personnel at the fulfillment centers weigh and measure each of your products that arrive through an inbound transfer. This weighing and measuring is referred to as the First Article Inspection. The weight and measurements from the First Article Inspection are found in the Shopify Fulfillment Network section of your product variant page in your Shopify admin, or in the SFN app.
The weights and measurements taken during the First Article Inspection are the values that are used when determining your billing.