How Big Can Your Backpack Get In Borderlands?

How Big Can Your Backpack Get In Borderlands? In summary after completion of playthrough 1 and the DLCs there is a guaranteed total backpack capacity of 48, with a maximum possible capacity of 51 (if Claptrap Rescue: Lockdown Palace provides a backpack SDU). Is there a storage in Borderlands 1? The Bank or Marcus Bank