Waterproof sleeve generally refers to wall penetration sleeve. The wall penetration sleeve is also known as wall penetration pipe, waterproof sleeve, and pre-buried wall pipe. Waterproof sleeves are divided into rigid waterproof sleeves and flexible waterproof sleeves. In electrical applications for electrical conduction, it is called AC wall penetration sleeve. It can be categorized by material into dry-type capacitor AC wall penetration sleeve and porcelain-insulated AC wall penetration sleeve, abbreviated as silicone rubber sleeve and porcelain sleeve, respectively.