Heatshrink tubing offers the folowing benefits to pvc wrapped wiring bundles :
There are many variations of heatshrink. Key properties to look out for :
DR25 is the king of motorsport heatshrink. Very flexible, high 2:1 shrink ratio and as the name says, Diesel Resistant. Availabe in imperial sizes from 1/8th to 1/2 inch. Other sizes available on request.
A close second in performance is RNF. Not quite as flexible is has a thinner wall that makes it well suited smaller areas. Also 2:1 shrink ratio and witha very good abrasion and chemical resistance. This can be used nearly every where except fuel and solvents are present.
ATUM is an adhesive lining that melts at around 100 degrees. This makes it suitable for joints and sealing the back of simple connectors. 3:1 shrink ratio.