The displayId read-only property of the VRDisplay interface returns an identifier for this particular VRDisplay, which is also used as an association point in the Gamepad API (see Gamepad.displayId).
The hardwareUnitId read-only property of the VRDevice interface returns the distinct hardware ID for the overall hardware unit that this VRDevice is a part of. All devices that are part of the same physical piece of hardware will have the same hardwareUnitId.
The recommendedFieldOfView read-only property of the VREyeParameters interface describes the recommended field of view for the current eye — ideally based on user calibration.
The renderRect read-only property of the VREyeParameters interface specifies the viewport of a canvas into which visuals for the current eye should be rendered.