Q7457A is the HP 4500 Black Bulk Ink Supply.  350ml delivered ink.
Q7456A is the HP 4500 Black Cartridge Connector.

Sharp, crisp print quality with minimal intervention, on primarily uncoated substrates
• High-quality, sharp, crisp output
• Excellent barcode readability
• Fade and water resistance on a variety of substrates

Best pricing, customer service and delivery available at www.inkpronto.com