You cannot add "HP Z4 G4 Workstation - 1 x Core X-Series i9-10900X - 8 GB RAM - 256 GB SSD - Mini-tower - Black - Windows 10 Pro 64-bit - Serial ATA/600 Controller - 0, 1, 5, 10 RAID Levels - English Keyboard - Gigab" to the cart because the product is out of stock.