I've used a 64 GB flash drive divided into two 32 GB partitions to allow me to install OS X Yosemite, and macOS Sierra which are the two Mac OS's used on our Mac's here at home.
Anyị ejirila 64 GB flash mbanye kesara abụọ 32 GB partitions iji kwe ka anyị wụnye OS X Yosemite na macOS Sierra nke bụ Mac Mac abụọ eji na Mac anyị ebe a n'ụlọ.