Waterproof sleeve, also known as wall penetration sleeve or penetration pipe. Flexible waterproof sleeves are generally used in structures where pipes pass through walls and are subject to vibration or have strict waterproofing requirements. After local processing of the sleeve, a primer coat (including linseed oil or cold bottom oil) is applied to its outer wall. Waterproof sleeves are divided into rigid waterproof sleeves and flexible waterproof sleeves. The main difference between the two is their primary application; flexible waterproof sleeves are mainly used in places like civil air defense walls and ponds with high requirements, while rigid waterproof sleeves are typically used in underground pipelines where pipe架ing is required.