The effects of material properties on the tankage fraction are apparent: to provide a small tankage fraction, we wish for: the material composing the vessel walls to be light (small ρ v ) and strong (large σ y ). the adsorbent material to be light (small ρ ads ), strongly adsorb xenon (large K), and have a large number of xenon adsorption sites packed per volume (large Mρ ads ). Note that the first and last wishes compete.