All dimensions in RasMol, such as radii and distances, may be specified in either 'RasMol units' or ┼ngstroms (┼). The RasMol units were first introduced to allow reasonably sized values to be specified for most of the operations performed in RasMol. A single RasMol unit corresponds to 1/250th of an ┼ngstrom; therefore the most frequently used values are in the hundreds. For this reason, if RasMol is given a distance parameter that does not contain a decimal point, it is assumed to be in RasMol units. For example, the command 'spacefill 300' specifies a sphere radius of 300 RasMol units, or 1.2 ┼.
However, dimensions within RasMol can also be specified in ┼ngstroms by placing a decimal point in the number. For example, 'spacefill 1.2' specifies a sphere radius of 1.2 ┼. This is particularly useful for the cut-off distance parameter in 'within' expressions.