The kernelUnitLengthX read-only property of the SVGFESpecularLightingElement interface reflects the x value of the kernelUnitLength attribute of the given <feSpecularLighting> element.
The kernelUnitLength attribute indicates the intended distance in current filter units, specified by the primitiveUnits attribute, for the x and y coordinates. It contains one or two values, with the y value defaulting to x if not present, and the kernelUnitLengthX property gets and sets the first value.
An SVGAnimatedNumber object that corresponds to the X-component of the kernelUnitLength attribute of the given element.