When an isotope is naturally occurring, its abundance found in nature is given and the isotope selection bar is color-coded black for easy recognition. The nuclei with significant yield in 235-U thermal neutron induced fission are also color coded with the symbol "FF" next to its symbol.
To use the Wallet Cards, either scroll through the list, or refine your search through the filter at the top of the list. All isotopes of a given element are then listed, any of which may be expanded to reveal the properties. Buttons at the bottom make it easy to advance forward or backward in atomic number, or return to the starting point.