Step 1. find a correct tubes with ID larger than the wire and cables OD.
Step 2. cover the wire or cable by tubes, then heat the tube by heat gun, finally the tube will shrink to the cable closely.
What is heat shrink tubing made of?
Heat shrink tubing can be made of any one of a range of thermoplastics, including polyolefin, Viton® (for high-temp and corrosive environments), polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP) and Kynar®. In addition to these polymers, some types of special-application heat shrink can also include an adhesive lining that helps to bond the tubing to underlying cables and connectors, forming strong seals that can often be waterproof. Another material that is sometimes added to heat shrink tubing is conductive polymer thick film, which provides an electrical connection between the two or more conductive objects that are being joined by the tubing – without the need to solder them first.