maskBorderSlice
The mask-border-slice CSS property divides the image set by mask-border-source into regions. These regions are used to form the components of an element's mask border.
Syntax: <number-percentage>{1,4} fill?
Initial value: 0
| Chrome | Firefox | Safari | Edge | IE |
| :------------------------------------: | :-----: | :----------------------------------: | :--: | :-: |
| 1 _(-webkit-mask-box-image-slice)_ | No | 17.2 | n/a | No |
| | | 3.1 _(-webkit-mask-box-image-slice)_ | | |Content copied to clipboard