What is the difference between a Heavy Duty and Standard Duty Fan Belt?

Heavy Duty Fan Belts have 3 unique features separating it from Standard Duty Fan Belts.

1. Notches are molded into the belt during manufacturing which increase flexibility and reduces bending stress. 
2. The belt edge is machined for even sheave groove contact resulting in smoother running, less slip and wear.
3. Patented Ethylene material construction provides –70 degree F to +250 degrees F temperature range to resist belt cracking.