FusionGsm V5

I have a question wile most roms are about 1 gb or so why is FusionGsm V5 only 3.46 mb i really want to try this rom but it is not the correct size as all the other roms i have used i cant post in the fusion rom thread so i figured the q&a was the place for this ? anyone know why its on ly 3.46 mb