ethics – contingent fee

hi,
please help to understand the issue of contingent fee –
study materials are clear: contingent fee is not allowed
but
Code of ethics says:
240.3 Contingent fees are widely used for certain types of non-assurance
engagements.
They may, however, create threats to compliance with the
fundamental principles in certain circumstances. They may create a self-
interest threat to objectivity. …

so, contingent fee is not allowed?
or

240.3 Contingent fees are widely used ?

thank you,

OLga