Black tube 4mm diameter

slide over wire(s) and shrink with soldering iron or lighter flame

shrinks down to grip and tidy

heat activated glue lining

shrink ratio 4:1 should be capable of shrinking down to 1mm diameter

sold per 150mm but cut to length ordered and not into

15cm pieces

note that most heat shrink tube is a 2:1 shrink ratio and not glued

so this is better.