Need for meeting requirements per FDA 21 CFR

You need to be in partial compliance with FDA 21 CFR, the part that considers purchasing process, production, quality control, and storage. In your case, you are providing outsourced services for your client. From both Fda or ISO 13485 standpoint of view, your client is responsible for your part of the process. It means that your clients need to have a quality agreement with you, and you need to have procedures and records that will prove that your part of the production is performed in compliance with specific requirements from the ISO 13485 or FDA 21 CFR. 

How this quality agreement looks like, you can see here:

• Quality Agreement for Subcontractor  https://advisera.com/13485academy/documentation/quality-agreement-for-subcontractor/