This International Standard has been drawn up to help manufacturers declare the weight (mass) of Reciprocating Internal Combustion (RIC) engines. This International Standard can be used: a) in conjunction with a standard dealing with engine power (e.g. ISO 3046-1, ISO 14396) drafted in accordance with the ISO-Core-Satellite-Concept principle so as to become a complete standard. NOTE ISO 15550 is the Core Standard and contains the requirements that are common to all engine applications. b) as a stand-alone document. ISO 3046-1 and ISO 14396 have been published as Satellite Standards. The next editions of ISO 1585, ISO 2534, ISO 8665, ISO 9249 and ISO 4106 will, as Satellite Standards, also belong to the ISO-Core-Satellite family.