usb flash drive - Is it possible (...how?) to have a single bootabe USB with a choice of OS installs

Is it possible to have a single bootable USB key with several install images E.g. for Windows 7, 8 and 10, and be able to choose which of these installs to boot?
If so how to set this up on the USB key.
Clarification: I don't want to run different windows from the USB - I just want to run one of the different installers. I.e I want to boot from the USB and choose to install a particular flavor of windows.

Answer

Yes, it is possible, by using a tool that installs Grub or Syslinux on the USB.
This is because Windows by itself does not support it.

Here are some free products that can create a Multiboot USB :