The 4 inch Rack Grease Containment System is perfect for most standard volume exhaust fans. It's versatile, easy to install, and budget-friendly. The rack has a built-in drain that allows water to pass through the system at a high volume. After the initial installation of the rack system, only the grease pillow needs to be replaced. That can be done during regularly scheduled hood cleanings depending on the volume of the restaurant. The 4 inch Rack System comes ready to install and includes a mounting bracket and deflector shield. For high volume / high grease producing fans, consider using the 7 inch Rack Grease Containment System. (1) absorbent pillow included WARNING : This product can expose you to chemicals including Cobalt Metal Powder and 1,3,5-Triglycidyl-s-triazinetrione, which is known to the State of California to cause cancer. For more information, go to www.P65Warnings.ca.gov .