This is PET expandable braided flex loom 
Black color
Sold by the foot 

 - Flex loom is a unique material what is like a plastic woven loom. When you cut it you will need to slightly melt the edges to keep it from unraveling. I use a small torch but you can also use a hot knife or a lighter. Be very careful when cutting this stuff that it doesnt unravel too much before you either melt the ends, tape, or heat shrink over it.
 
- Also because of the woven style and how it expands in girth it will slightly loose some of the length. So for larger cables you will want to anticipate the shrinkage and order more than you truely need so that it doesn't come up too short.
 
Here is the fit guide with the cables that I sell:
1/2" Flex Loom fits 1/0 and 2/0 awg cables
3/8" Flex Loom fits 6, 4, and 2g cables
1/4" Flex Loom fits speaker wire and 8g cables.