Adding to previous posts, one other factor to consider are the regulations about supplier selection and management in 21 CFR 830.50. FDA scrutiny on supplier selection, criteria used, and more importantly how sponsors control their supplier has increased in the last few years. It is one of the first topics discussed during audits. Contracts should be written in a way that clearly defines roles and responsibilities, and robust inspection plan that ensures materials/services provided by vendors meet specifications (that is also part of the contract)!