OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade. OWC DIY Kit for all Apple iMac 2011 Models for replacing the main hard drive. Hard Drive Upgrade Kit for all Apple iMac 2011 Models for replacing the main hard drive. Includes all cables and tools necessary for installation. Hard drive sold separately. Eliminate fan noise and maintain correct system fan control when upgrading your 2011 iMac. The only iMac HDD upgrade option on the market certified to pass the Apple Hardware Test. Fixes firmware incompatibility issues with third party hard drives. Engineered in-house and backed by OWC's award-winning customer support. Improve Performance and Capacity. Upgrade Your iMac with Confidence. OWC's in-line solution is the only hardware digital thermal sensor on the market allowing a third-party SATA drive to be installed in your iMac. A convenient, plug-and-play cable, the In-line Digital Thermal Sensor eliminates fan noise and maintains proper system fan control through the iMac's System Management Controller. This innovative device is designed specifically for the iMac, requires no software hacks and ensures compatibility with Apple's built-in diagnostic processes. Note: Before attempting to perform this installation, please watch the OWC Install Video, corresponding to your machine, in its entirety to determine your ability to perform this complex upgrade. Compatibility: 2011 iMac 21.5 inch (Model ID: iMac12,1) 2011 iMac 27 inch (Model ID: iMac12,2)