The Lenovo Cooling Fan Pack B 81M4 is a cooling solution specifically designed for Lenovo devices to maintain optimal operating temperatures during extended use. This cooling fan unit features a compact design with dimensions of approximately 120 mm x 120 mm x 25 mm and weighs around 180 g, allowing for integration into various Lenovo system configurations. The fan operates at speeds ranging from 800 to 2200 RPM and provides an airflow of up to 55 CFM with noise levels below 28 dBA for quiet operation. Its construction with durable materials, including a concealed plastic housing and precision-balanced blades, ensures reliable heat management and extended component lifespan. The fan comes with a 4-pin PWM connector for precise speed control and a ball bearing system with a lifespan of over 60,000 hours of continuous operation. The operating temperature range extends from 0°C to 70°C with a maximum static pressure of 2.8 mmH₂O for effective heat dissipation. This replacement cooling unit is compatible with multiple Lenovo desktop and workstation models, providing consistent airflow to prevent thermal throttling and maintain system stability during demanding computing tasks. The anti-vibration mounting system minimizes resonances and ensures secure installation, while the dust-resistant design preserves performance over time. This cooling solution meets industry standards for electromagnetic compatibility and features reverse polarity protection for enhanced reliability.