The document provides guidelines for specifications of new drug substances and products. It discusses setting specifications based on development data and stability studies. Universal tests for drug substances include identification, assay, impurities. For products, additional tests depend on dosage form and may include dissolution, uniformity, sterility. The guidelines provide concepts for justifying specifications and periodic testing. They apply principles for biotech products, addressing characterization, analytical validation, process controls, and linking specifications to manufacturing and clinical data.