Your search for "ap7721" revealed the following:
For APC AP7721 AP7722 AP7750 AP7750A AP4423 ATS Ears Rack Mount Bracket Kit
SKU: NSB-6313
Condition: New
Shipping: Overnight Options
Warranty: 365 days
$ 24.99
• 247 in stock
Call if you need more
APC AP7721 12x C13, 208V or 230V Automatic Transfer Switch
SKU: NSH-2469
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
NEW APC AP7721 12x C13, 208V or 230V Automatic Transfer Switch
SKU: NSN-3201
Condition: New
Shipping: Overnight Options
Warranty: 365 days