Waterproof sleeve generally refers to wall penetration sleeve. Wall penetration sleeve is also known as wall penetration pipe, waterproof sleeve, pre-buried wall pipe. Waterproof sleeves are categorized into rigid waterproof sleeve and flexible waterproof sleeve. In electrical applications for electrical conductivity, it is called alternating current wall penetration sleeve. Depending on the material, it can be divided into dry-type capacitor-type alternating current wall penetration sleeve and porcelain-insulated alternating current wall penetration sleeve, abbreviated as silicone rubber sleeve and porcelain sleeve, respectively.