2x heat shrinkable tubing, i.e., heat shrinkable sleeve, is a new type of environmentally friendly halogen-free flame retardant sleeve, the product is of high quality and low price, and can provide insulation protection for wires, cables and wire terminals. It has the characteristics of low temperature shrinkage, soft flame retardant, insulation and anti-corrosion. It is widely used in the insulation protection of various wire harnesses, solder joints, inductors and the anti-rust and anti-corrosion of metal pipes and rods. The shrinkage ratio of heat shrinkable tubing is 2:1 inner wall without glue, which is used in electronics, communications, automobiles and other fields to provide insulation protection for wire connections and protect the surface of metal products from rust.