Republican Sinn Féin and Provisional Sinn Féin were formed in 1986, when Sinn Féin split over the issue of taking Dáil seats. They reject the Belfast Agreement and support the use of force; the poster above calls for political status for prisoners, the same issue that led to the blanket protest and hunger strikes. (Their web site is in fact republicansinnfein.org; they are also on Twitter.)