How do I know that all items are on GSA Federal Supply Schedule?

In providing a total solution to an agency’s requirement under a Contractor Team Arrangement (CTA), the services and products proposed should be identified under each team member’s GSA Schedule contract. Any proposed services and products that are not part of a GSA Schedule contract (i.e., open market items) may be included only after all applicable acquisition regulations have been followed (see Federal Acquisition Regulation 8.401(d)) and must be clearly labeled as such.