Pair bundles: Bundles Monk docs

A pair bundle joins one main product to one add-on product. When a cart holds both, checkout discounts the pair.

Defining one

Pair bundles are created on the Bundles page. Each one takes:

Main product. The product a buyer adds first. The bundle is stored against this product, so one product can be the main product of exactly one pair.
Add-on product. The product discounted when it shares a cart with the main product. It has to be a different product from the main one.
Discount. Use store default, Percentage off, or Fixed amount off. A percentage cannot be more than 100, and a value has to be greater than zero.
Applies to. Add-on product only (the default) or Both products.

Saving over a product that already has a bundle replaces that bundle rather than adding a second one.

When it qualifies

The cart has to hold at least one line of the main product and at least one line of the add-on product at the same time. Nothing else is required:

Quantities do not matter. One of each is enough, and more does not increase the discount rate.
Order of adding does not matter.
If either half leaves the cart, the discount goes with it.
A product that names itself as its own add-on is ignored, since that pair could never be anything but the product on its own.

What it discounts

The discount is applied to cart lines, not to the order total.

With Add-on product only, every cart line of the add-on product is discounted.
With Both products, every cart line of both products is discounted.

A percentage takes that percentage off each targeted line. A fixed amount is taken off the targeted line once, not once per unit.

Several pair bundles in one cart all apply. Two unrelated pairs both get their discount.

Which value is used

The bundle’s own discount is used when it is readable and greater than zero. When the bundle is left on Use store default, or its value cannot be read, the store default reward is used instead. If neither is usable, the pair is skipped and nothing is discounted.

The targeting choice and the value are read independently, so a bundle with a mistyped value still applies to the products you chose, using the store default value.

The buyer preview

While you edit a bundle, the panel beside the form shows the pair’s base price, the price after the discount, and the total. If both products carry a cost per item in Shopify, it also shows cost, profit and margin for the discounted pair. Nothing there is saved; it is a calculator.

What buyers see

On a product page carrying the storefront block, a pair bundle renders as a card headed “Buy it with add-on”, with the saving as a badge, a hint about what is missing, and a button reading “Add both to cart” or “Add product to cart” depending on what the cart already holds. Once both are in the cart the card reads “Bundle complete. Discount applied at checkout.”

At checkout the discount appears against the discounted line, labelled “Bundle discount”.