This short presentation tells the story behind the CHL-16/B1SF4 and CHL-20/B1SF4 bellow mechanical seals designed for CNP CHL/CHLF series horizontal pumps. You'll see how these balanced rubber bellow seals handle temperatures from -30°C to 200°C, pressures up to 0.3MPa, and speeds up to 5m/s in water applications. We'll walk through the material composition featuring ceramic/SiC rotary rings, carbon stationary rings, and stainless steel components, plus demonstrate their installation and performance capabilities for industrial pump systems.