This product is either discontinued or we cannot get that from suppliers.
Cisco AIR-CT8540-K9 8540 Wireless Controller, Rack-mountable - 2U, Processor 1 x Intel Xeon E5-2680v3 - 2.5 GHz, System Memory 64 GB, Hard Drive 240 GB x 2 - SATA 6Gb/s, 10 Gigabit Ethernet, Throughput 40 Gbps, Wireless clients 64000.
The Cisco 8540 Wireless Controller is a highly scalable, service-rich, resilient, and flexible platform that enables next-generation wireless networks for medium-sized to large enterprise and campus deployments.