The document summarizes a scheme for distributing monthly liquid samples for external quality assessment. It includes mainline chemistry analytes distributed in 3.5ml and 1ml aliquots. The material is human serum manufactured to high specifications and sterilized to maintain integrity and commutability. Reference target values are assigned for key analytes to assess traceability. Performance reports identify components of imprecision and inaccuracy, and provide group reporting in graphical and tabular form to manage performance across sites. The scheme also includes samples for assessing linearity, validating new equipment and methods, and challenging laboratories.