Ilford rapid fixer has for quite a while had a confusing label that refers to "Ilford Paper fixer" inside. Ignore that label.
There is a page on http://www.ilfordphoto.com/products/...ndry+Chemicals which should allow you to download the data sheet for the Product, (the page gives a popup link which I could not access)
(try http://www.darkroom.ru/info/manuals/...manual_eng.pdf ) Sugused for film is 1+4 mix (One part Concentrate to 4 parts water) with a time of 2-5 minutes, any film with Delta or Tmax in it's name should be fixed AT LEAST 5 minutes in fresh fixer.
All the "T-Grain" or Delta Grain films require more time than given.