Patch Cards in Mega Man Battle Network 5
From The Rockman EXE Zone Wiki
Using the e-Reader+, both versions of Rockman EXE 5 can scan e-Reader cards to further customize their MegaMan, as well as other features.
Information
e-Reader Cards (Known in game as Mod Cards) can be used to enhance your MegaMan with Abilities not possible normally. Unlike how Mod Cards worked in the EXE 4, with slots for cards, EXE 5 and 6 Introduced an MB system. Each card now has a certain MB value, with MegaMan having a limit of 80 MB. Cards with higher MB generally have better Ability, and previous cards must be deleted when wanting to scan cards. Individual cards can be turned on or off when needed, but this does not lower the MB limit.