05 altima interior speaker size?

Hi people, another question i have to ask.I plan on changing all interior speakers in my car, does anyone know the proper size speakers?I went to crutchfield, but it shows diff size speakers for the front, back and so forth.It also says that no speakers fit my rear deck(theres speakers there), and i believe there 6x9s there, any info would be greatt, thanks.

humm, , can you see them from looking up in the trunk??  Maybe measure them.   Id put  a 6.5" coaxial set in there if there originally 6x9's, seal off the speakers with a box or something for each one so the subs do screw them up.   Im also betting that the fronts are 6.5" components stock.      2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.