Tissue thickness compensator comprising a plurality of layers

A fastener cartridge for a surgical instrument, the fastener cartridge comprising:

• fasteners movable between an initial position and a fired position;
• fastener cavities configured to hold said fasteners when said fasteners are in said initial position;
• and
• a tissue compensator comprising:
• a first spring layer;
• a second spring layer;
• a gap between said first spring layer and said second spring layer, wherein at least one fastener is configured to move through said gap and compress at least a portion of said tissue compensator when said fastener is moved to said fired position.

An end effector assembly for a surgical instrument, the end effector assembly comprising:

• an anvil;
• a thickness compensator comprising:
• a first compensation layer;
• a second compensation layer;
• and
• a pocket positioned between said first compensation layer and said second compensation layer;
• and
• a fastener cartridge comprising a fastener, wherein said fastener is moveable between an initial position and a fired position, wherein at least a portion of said fastener is configured to pass through said pocket when said fastener is moved to said fired position, and wherein said fastener is configured to compress said thickness compensator when said fastener is moved to said fired position.