Brake Kit question..

[project85t-top]

im looking at a few diff brake kits for my stang. i came across this one. i liked it over all cause of the price but am a bit confused about something. its the Drag Race Disc brake Kit from Aerospace Components. the 4 piston kit. the front rotors are 10.25" and the rears are 11.375". my question is why are the rears bigger on this kit? also does anyone have this kit on their car? thanks...