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# How to apply custom discounts using Product (line) attributes + easy bundle builder example

${youtube}[How to apply custom discounts using Product (line) attributes + easy bundle builder example](GdXhawJHct0)
This guide explains how to use the **product line attributes** rule to create a highly specific discount that applies only to products added to the cart via a third-party app, such as a product bundle builder.

### Introduction: What are Product Line Attributes?

Product line attributes are hidden properties or data attached to an item when it's added to the cart. Apps like bundle builders use these attributes to identify which products belong to a specific bundle. By targeting these attributes, you can create a discount that applies *only* when a customer buys the bundle, not when they buy the products individually.
For this example, we will assume a bundle app adds an attribute with the `key` of `bundle` and a `value` matching the bundle's name (e.g., `PDP1`).

### 1. Start with the Custom Discount Builder

1. In the Kite app, select the **Custom Discount Builder**.
2. Give your campaign a name (e.g., `bundle-discount`).

### 2. Configure the Discount for the First Part of the Bundle

1. In the first option block, go to the **"Discountable Products"** section.
2. **Rule 1 (Product Identity):** Set the first rule to identify the products. For example, choose `Collections` and select the "Hydrogen" collection.
3. **Rule 2 (Bundle Identity):** Click to add another rule and select **"product line attributes"**.
    * Enter the attribute key: `bundle`
    * Enter the attribute value: `PDP1`
4. Ensure the logic is set to **"All rules should apply"**. This is crucial because it means the product must be from the "Hydrogen" collection *and* have the `PDP1` bundle attribute.
5. Set your offer for these items (e.g., **Fixed price** of `₹100` each).

### 3. Configure the Discount for the Second Part of the Bundle

If your bundle has multiple steps or parts, create a new option for each.
1. Click to add a new option.
2. In the **"Discountable Products"** section for this new option, repeat the process:
    * **Rule 1 (Product Identity):** Select the products for the second part of the bundle (e.g., the "Oxygen" collection).
    * **Rule 2 (Bundle Identity):** Add the same **"product line attributes"** rule (key: `bundle`, value: `PDP1`).
3. Ensure the logic is set to **"All rules should apply"**.
4. Set the offer for this second set of items (e.g., **Fixed price** of `₹200` each).

### 4. Save and Test

1. Click **Save**.
2. Go to your store's custom bundle page (not the individual product pages).
3. Select items from both steps of the bundle and add them to your cart.
4. In the cart, verify that the correct fixed prices (`₹100` for the "Hydrogen" items and `₹200` for the "Oxygen" items) have been applied.