Magento customer segment by past purchase history

I wanted to fulfil the following use case:
Create a customer segment based on past purchase history. If a user has purchased SKU-X, they are to belong to a given customer segment.
The problem was, I could not remember why the SKU was not listed in the drop downs while adding a condition in the purchase history.
Enabled “Use for Promo Rule Conditions” on the “SKU” attribute; it allowed “SKU” to show up in the promotional drop downs.