Your search for "AP7921" revealed the following:
For APC AP7900 AP7800 AP7901 AP7921 AP7920 NT-AP7900-RM Rack Mount Bracket Kit
SKU: NSB-6142
Condition: New
Shipping: Overnight Options
Warranty: 365 days
$ 24.99
• 65 in stock
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APC AP7921 Switched Rack 200V,208V,230V 20A 8x IEC 60320 C13 1U PDU
SKU: NSH-0154
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
APC AP7921B Switched Rack 200V,208V,230V 20A 8x IEC 60320 C13 1U PDU
SKU: NSB-9857
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days