Stapling system comprising a lockout

1. A stapling assembly system for use with a surgical stapling instrument, said stapling assembly system comprising:

a shaft portion comprising a proximal end operably engageable with the surgical stapling instrument;

a first replaceable cartridge jaw, comprising:

a first top portion configured to support tissue;

first staple cavities defined in said first top portion;

a first bottom portion;

first staples removably stored in said first staple cavities;

a first sled movable between an unfired position and a fired position;

first staple drivers configured to eject said first staples from said first staple cavities; and

a first retainer extending around said first bottom portion configured to prevent said first staple drivers from falling out of said first replaceable cartridge jaw through said first bottom portion;

a second replaceable cartridge jaw, comprising:

a second top portion configured to support tissue;

second staple cavities defined in said second top portion;

a second bottom portion;

second staples removably stored in said second staple cavities;

a second sled movable between an unfired position and a fired position;

second staple drivers configured to eject said second staples from said second staple cavities; and

a second retainer extending around said second bottom portion configured to prevent said second staple drivers from falling out of said second replaceable cartridge jaw through said second bottom portion;

a second jaw comprising an anvil configured to deform said first staples and said second staples;

a firing member configured to engage said first staple drivers during a first firing stroke of said firing member and said second staple drivers during a second firing stroke of said firing member; and

a lockout configured to selectively prevent said firing member from being advanced through a said firing stroke.

2. A re-usable loading unit system for use with a surgical stapling instrument, said re-usable loading unit system comprising:

a shaft portion comprising a proximal end operably engageable with the surgical stapling instrument;

a first replaceable cartridge, comprising:

a first top portion configured to support tissue;

first staple cavities defined in said first top portion;

a first bottom portion;

first staples removably stored in said first staple cavities;

a first sled movable between an unfired position and a fired position;

first staple drivers configured to eject said first staples from said first staple cavities; and

a first retainer extending around said first bottom portion configured to prevent said first staple drivers from falling out of said first replaceable cartridge through said first bottom portion;

a second replaceable cartridge, comprising:

a second top portion configured to support tissue;

second staple cavities defined in said second top portion;

a second bottom portion;

second staples removably stored in said second staple cavities;

a second sled movable between an unfired position and a fired position;

second staple drivers configured to eject said second staples from said second staple cavities; and

a second retainer extending around said second bottom portion configured to prevent said second staple drivers from falling out of said second replaceable cartridge through said second bottom portion;

a second jaw comprising an anvil configured to deform said first staples and said second staples;

a firing member configured to engage said first staple drivers during a first firing stroke of said firing member and said second staple drivers during a second firing stroke of said firing member; and

a lockout comprising a locked configuration and an unlocked configuration configured to selectively prevent said firing member from being advanced through a said firing stroke.