def cuboid(target, throat_diameter='throat.diameter', throat_length=
    'throat.length'):
    """
    Calculate surface area for a cuboid throat

    Parameters
    ----------
    target : OpenPNM Object
        The object which this model is associated with. This controls the
        length of the calculated array, and also provides access to other
        necessary properties.

    throat_diameter : string
        Dictionary key to the throat diameter array.  Default is
        'throat.diameter'.

    throat_length : string
        Dictionary key to the throat length array.  Default is 'throat.length'.

    Returns
    -------
    value : NumPy ndarray
        Array containing throat surface area values.

    """
    return 4 * target[throat_diameter] * target[throat_length]
