Remnant inventory refers to the ad inventory that is sold at discounted wholesale prices to different ad networks. The excess supply and forecasting problems with ad inventory results in remnant inventory. In other words, ad inventory that is not sold through in-house sales teams are remnant inventory. They dont come with guaranteed delivery. Advertisers purchase remnant inventory from huge networks for use in CPC, CPA or CPM marketing programs. Even though premium inventory is highly regarded, remnant inventory is not inferior in any way. In fact, previously premium inventory becomes remnant inventory due to the decline in demand.