HP 0231A81B - Spare 7502 fan tray assembly - Includes three 92mm x 92mm (3.62in x 3.62in) fans - Produces maximum air flow of 165CFM Retail
HP 0231A81A - Spare 7503 fan tray assembly - Includes six 92mm x 92mm (3.62in x 3.62in) fans - Produces maximum air flow of 330CFM Retail
HP 0231A81C - Spare 7506 fan tray assembly - Includes nine 92mm x 92mm (3.62in x 3.62in) fans - Produces maximum air flow of 495CFM Retail