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# How to Set NMFC Numbers with Shopify Metafields

Shipduo adds **NMFC** and **NMFC Sub** metafields to your Shopify products automatically when you install the app. Add the product's NMFC number and NMFC sub to **automatically apply the correct freight classification details during checkout and shipment booking**.
When these fields are populated, Shipduo uses them to **prefill the NMFC information on rate requests, shipment details, and BOLs** — helping improve rating accuracy and reduce manual entry.
> 📋 **Good to know:** These metafields are created for you on install. You just enter the values on the products you want to control.

## What These Metafields Do
* **NMFC** — the National Motor Freight Classification item number for the product.
* **NMFC Sub** — the sub-number that goes with it.
When both are populated on a variant, Shipduo applies the correct freight classification automatically — prefilling the NMFC details on **rate requests at checkout** and on **shipment details and BOLs** at booking. If you leave them blank, Shipduo determines the freight class on its own (based on dimensions and weight).

## Where to Find Them
1. In your **Shopify Admin**, go to **Products** and open a product.
2. Scroll to the **Variant metafields** section (or open an individual variant).
3. Locate the **NMFC** and **NMFC Sub** fields.
> ![](https://storage.crisp.chat/users/helpdesk/website/-/f/8/1/5/f8152ba4a1e1a800/screenshot-2906-072451-pm_f89nj.jpg)

## How to Set Them
1. Open the product (and the specific **variant**) in your Shopify Admin.
2. Enter the product's number in the **NMFC** field.
3. Enter the matching value in the **NMFC Sub** field.
4. Click **Save**.
That's it — Shipduo will now prefill these numbers wherever the product is rated and booked.

## Why Use This
* **Improved rating accuracy:** the correct freight classification is applied consistently at checkout and booking.
* **Less manual entry:** the NMFC details are prefilled on rate requests, shipment details, and BOLs, so there's nothing to re-type.
* **Consistency end to end:** the same classification flows from the customer's checkout quote through to the BOL.
> 💡 **Tip:** Use this for products with a known, fixed NMFC classification. For items where you'd rather let Shipduo determine the class from dimensions and weight, simply leave these fields blank. For related setup, see *How to Set Up Shipduo Routing Metafields in Shopify*.

## Troubleshooting
* **Don't see the NMFC fields?** They're added automatically when the Shipduo app is installed. If they're missing, confirm the app is installed, or add the metafield definitions manually (see *How to Add Dimensions to a Shopify Metafield* for how to use **Add definition**).
* **Your NMFC isn't being prefilled?** Make sure **both** NMFC and NMFC Sub are filled in correctly on the variant.
* **Need help?** Chat with us or contact Shipduo Support.