The Firenze Card grants admission to the major museums, villas and historical gardens in Florence. It is promoted by the Municipality of Florence, the Ministry for the Arts and Cultural Activities, the Regional Direction of Cultural Heritage, the Special Superintendence for Historical, Artistic and Ethnic-anthropological Heritage and for the Museum Circuit of the city of Florence, the Province of Florence and the Chamber of Commerce of Florence, in collaboration with ATAF.
The Firenze Card is valid for 72 hours and provides you the admission only once to all museums of the Circuit, located in Florence. It entitles you to visit permanent collections, exhibitions and other activities held in these museums, but missing is (for example) the Opera del Duomo, the Chiesa di San Lorenzo and Santa croce, the Capella Spagna. You will avoid queues and booking limitations. You are also entitled to use public transports free of charge. Every card grants free access to museums and means of transportation to a second person if younger than 18 (but EU citizens only!!!).
Alternative you should consider the amici degli Uffizi card which grants the admission to 22 sites within one calender year for € 60/person or € 100 for a family of four.