At our store we are setting up our shipping on Shopify. When setting up our rates we are curious if we need to put the exact weight in for all of our products, or can we use the dimensional weight from our boxes ((LxWxH)/166)?

Is inputting the product weights necessary if you are doing a flat-rate shipping fee? Since we are not doing a weight based fee, and currently have many items, I am curious if we even need to put weight values on the products?