1) No effect to your Macbook and easy installation.
<br />2) Protect your laptop against dust and moisture.
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<br />3) Material: The case is plastic hard case 
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<br />About Model Number:
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<br />Please kindly check the model of your Macbook before purchasing!
<br />
<br />Note: If you're not sure the model, please kindly check the back of your macbook, you could see the model (Axxxx) printed there.
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<br />A. Pro 13'' A1278 (Have CD-ROM,2009-2012)t
<br />B. Retina Pro 13'' A1425 and A1502 NO CDROM
<br />C. Air 13 ''
<br />D. Air 11 ''
<br />D. Pro 15'' A1286 (Have CD-ROM,2009-2012)t
<br />E. Retina Pro 15'' A1398 NO CDROM
<br />F.Macbook 12 ''