> For the complete documentation index, see [llms.txt](https://docs.optis.me/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.optis.me/product-options/customize-design/how-does-product-option-sku-works.md).
# How does Product Option SKU works?
#### Where to add SKU for OPTIS options?
1. For all the **Text input** options, **Color picker, File upload, Font picker**, you can add SKU for OPTIS options in the **Option settings**:
2. For all the **Check list** options (except for Font picker) and **Swatch** options, you can add SKU for OPTIS options in the **Option values**:
#### How does it work with Shopify variants SKU?
When customer buys the product with both Shopify variants and OPTIS option, the SKU will show like this:
#### Can I customize the SKU display on cart page?
Yes you can choose to show Shopify variants SKU or OPTIS SKU or both to show with your products in the **Setting > General settings:**
.png?alt=media&token=338349b0-4646-459c-8240-954508e4179d)
.png?alt=media&token=089daa94-ab00-440f-811e-5b049bce087b)
.png?alt=media&token=10d41253-d9bb-4ce2-9567-abbb130c6847)