Insulators, also known as composite insulators, consist of an insulating element made up of a glass fiber resin core rod (or tube) and a jacket and skirt made of organic materials. They are characterized by their small size, light weight, high tensile strength, and excellent resistance to dirt and flashover. However, they are less resistant to aging than porcelain and glass insulators. Composite insulators include: rod-type suspended insulators, insulating crossarms, pillar insulators, and hollow insulators (i.e., composite sleeves). Composite sleeves can replace porcelain sleeves used in various electrical equipment, such as transformers, lightning arresters, circuit breakers, capacitive sleeves, and cable terminations. Compared to porcelain sleeves, they offer the advantages of high mechanical strength, light weight, and small size tolerances, and can also prevent damage caused by fragmentation.