Darknet Custom Firmware
Darknet 4.81 Standard v1.0 CEX
Darknet 4.81 Cobra 7.3 CEX v1.0
The Custom Firmwares are packed into a .zip file.
When the CFW is downloaded, launch MultiMAN and go on the File Manager (mmOS).
Now, all you need to dois a Double Click on the .zip File just downloaded (PS3~dev_usb000.zip).
Select 'YES' to the question.
It will extract the 'PS3/UPDATE/PS3UPDAT.PUP' Directory ready for the new CFW installation :)