The future definition of the kilogram is measured in a vacuum. Methods and equipment for storage and transfer of mass standards are presented. This white paper will be relevant to National Metrology Institutes (NMIs), Weights & Measures and private calibration laboratories, weight manufacturers and metrologists. It is also aimed at anyone who has an interest in progress to eedefine the kilogram, subsequent traceability to the mass scale, and the latest developments in storage and transfer technology for mass standards to support this research.