When sourcing land drainage pipes, the most critical technical factor is the Stiffness Class (SN rating). For standard agricultural use, SN4 is typically sufficient, while areas with heavy vehicle traffic or deep burial requirements necessitate SN8 or higher. You must also specify the material: High-Density Polyethylene (HDPE) is preferred for its superior chemical resistance and flexibility, whereas uPVC is common for rigid applications. Additionally, verify the perforation pattern (slotted or punched) to ensure it matches the soil permeability of the destination site.