Sizes currently available through these links include
measuring inner diameter. Convert between ring sizes with this Wikipedia article on ring sizes.
MOLA data forms the outer surface of the ring, modelling the topography of Mars between approximately 30 degrees north and south of the equator. Vertical scale is exaggerated by about 7 for clarity. Numerous surface features are visible, including Olympus Mons, the Tharsis volcanoes, Tharsis Tholus, Biblis Patera, Ceraunius Tholus, Noctis Labyrinthus, Hebes Chasma, Ganges Chasma, Valles Marineris, Eos Chasma, Xanthe Terra, Margaritifer Terra, Ares Vallis, the Watney triangle, Schiaparelli crater, Terra Meridani, Terra Sabaea, Huygens crater, Isidis Planitia, Syrtis Major, Libya Montes, Gale Crater, Elysium Mons, Albor Thous, Tyrrhena Terra, Hesperia Planum, Apollinaris Patera, and Pettit crater. Italic features may not be visible on smaller prints.
The inside of the ring consists of debossed icons of the Mars Pathfinder rover (Sojourner), the Mars Exploration Rover (Spirit/Opportunity), the Mars Science Laboratory (Curiosity), and a truncated hexa-octahedral magnetite crystal of the sort found in ALH84001 and the magnetotactic bacteria strain MV-1 - currently the strongest evidence in support of the hypothesis that life originated on Mars.
The ring is printed in high definition stainless steel (feature size 0.1mm) and may some require some burr removal with a small file for comfort.
Ring sizes are given by inner diameter in mm. This ring is unusually broad and inflexible, and you may need to convert from an existing ring size.
Rings come in many sizes and 3D printing requires a test print at each size. The Mars ring is now available in a variety of sizes, available via i.Materialise through the links above. If there is a size you want which is not available, please get in touch.