Generally, flexible waterproof cannulas for pipes pass through walls where shock exists and strict waterproof is needed. 
*When cannula needs to pass through, it meeting non-concrete walls, the walls shall be rebuilt by concrete, the cast concrete area shall be over 200mm, and the cannula shall be cast inside walls one-off. 
*The DN and wall thickness sizes shall be based on clients' demand, remember to clearly write diameter, pipe exterior diameter and wall thickness, etc.