With the developments in high-pressure technology and its integration with synchrotron radiation techniques, small and intense x-ray beams can be used for diffraction measurements on a small sample in helium environment in the diamond anvil cell. Together with loaded small ruby spheres in the same environment as pressure marker, high precision data have been obtained on the relations between pressure-induced specific volumes (V) of many materials and ruby fluorescence line shifts (lambda). Several ruby pressure scales have been already published, based on recently obtained V-lambda relations. Discrepancies among these recent ruby scales are within 2-3% for pressures up to 150 GPa. On behalf of the Task Group of International Practical Pressure Scale, we present a summary of our on-going discussions on this matter among the task group members, and propose a ruby scale, based on the following considerations: (1) it is based on experimental data without prior knowledge of pressure; (2) it includes data for ionic, covalent, and metallic materials; (3) it is easily traceable and amendable when better data become available; (4) it reasonably represents recently published ruby scales; and (5) it covers a pressure range up to 150 GPa.