OEM means that the part is the same part used within your device

Product description
Reviews
Part: Apple iPhone 5 LCD digitizer
Manufacturer: OEM (3M)
Condition: Factory new
Warranty: N/A (consumable)
Parts Origin - OEM

The term OEM stands for 'Original Equipment Manufacturer', the exact meaning differs in several industries.
To us, OEM means that the part is the same part used within your device, using the same materials and specifications.
We use the term OEM to cover many parts from refurbished, used and new components, the exact condition will be stated in the items description.
In some cases when the part supplied is made up to several components (for example an LCD assembly) the part may have been assembled by a 3rd party vendor using OEM parts meaning that consumable may differ (such as adhesive used)
Although strict testing procedures are put in place to ensure the quality of the part these testing practices and procedures may differ from the checks manufacturers use.
Any hardware supplied as OEM will not have any quality loss or loss of features and covered under our extensive returns policy.
As in many cases we dont obtain directly from the devices manufacturer, nor in some cases are we affiliated with device manufacturer in any way and they are not involved in the testing or sales process of the component we sell.