This is a single 4GB Ram chip upgrade for the Macbook and Macbook Pro Core 2 Duo models. THIS IS A SINGLE CHIP, NOT TWO CHIPS. Specs: 4GB DDR2 PC5300 SODIMM.

CORE 2 DUO Model Compatibility:

Can address up to 6GB:

Santa Rosa and Penryn Models : 2.2 GHz MacBook Pro 15"
2.4 GHz MacBook Pro 15"
2.5 GHz MacBook Pro 15"
2.6 GHz MacBook Pro 15"
2.4 GHz MacBook Pro 17"
2.6 GHz MacBook Pro 17"

Can address up to 6GB:

2.1GHZ Penryn (February 2008) 2.4GHZ Penryn (February 2008) 2.0GHz MacBook 13.3" (Late 2007 model)
2.2GHz Macbook 13.3" (Late 2007 model)