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 the outer wall. Waterproof sleeves are divided into rigid and flexible types. The main difference between them lies in their primary applications; 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 necessary.