double cab bed size

Excellent forum guys. I have an 03 TRD double cab and I am searching for a used capfor it. I just wanted to no if all the double cab tacomas have various size beds or do they come one standard size. I found a used cap and it lists that it is for a tacoma double cab with a 4 foot bed. My bed is about 5 foot 3 inces. Any help would be appreciated.