Customer Service:MT-VIKI provides 1 year's warranty and lifetime technical support. Any problems, please feel free to get support from us. Upgrades: 1.Four 2in1 professional hdmi/usb KVM cables included, no cable mess up. 2. Two switch options: extended desktop selector & manual button. Package includes: 1x KVM hdmi switch 4 ports, 1x Desktop selector, 1x Manual, 4 x special USB and HDMI cable (2in1, 4ft/1.2m), which makes your desk more cheaner. Please plug the HDMI cable w/ USB pigtail into computer port. Compatibility: this kvm switch 4 computers supports plug and play, no software required. Driver-free for Windows 10/8/8.1/7/Vista/XP and Mac OS, Linux. MT-VIKI HK04, 4 port KVM switch HDMI, allows you to switch 4 computers by only 1 set( monitor, keyboard, mouse). It can also share USB speaker, U disk or printer and USB 2.0). Also support Blue-tooth Keyboard & mouse with a usb receiver, 3D & EDID.