mask-border-width CSS property.

Values: [ <length> | <percentage> | <number> | auto ]{1,4}
Initial value: auto
Applies to: All elements. In SVG, it applies to container elements excluding the <defs> element and all graphics elements
Inherit: no
Percentages: relative to width/height of the mask border image area
Animatable: no
Media: visual
Computed value: all <length>s made absolute, otherwise as specified

CSS Standards

CSS 1
CSS 2
CSS 2.1
CSS 3
Yes