Silk satine gimp is a thick, shiny gimp thread that can be used for outlining and fill for grounds, trees, flowers, and water. It can be laid next to other outlining threads to vary texture. It is about 1 mm in diameter and is sold in 3 meter lengths. Use Japanese rice glue to treat the ends so they don't fray and you get a good cut as it can not be sunk into the ground fabric.
Pictures show it next to silk gimp, which is switchable, and silk serpentine which is similar in size.
You can purchase the entire 15-color collection on one click.