This part of IEC 61753 deals with performance standards for parts of fibre management systems. It defines those tests and severities which form the performance or general operating service environment, and identifies those tests which are considered to be product specific. Test and severity details are given. This part of IEC 61753 contains the minimum test and measurement severities which a specific product must satisfy in order to be categorised as meeting the IEC standard, Category U – Uncontrolled environment, as defined in Annex A of IEC 61753-1. More severe requirements may be agreed between the customer and the supplier. A product performance standard will contain a combination of those tests and measurements that are common to all products, for a particular service environment or performance category, and those that are considered specific to that particular product in that environment.