Item being sold is a bootable USB flash drive which has been loaded with the necessary installer package of macOS High Sierra 10.13.6.
With this flash drive, you can either use it to upgrade a system you currently have loaded with data (i.e. from Yosemite up to High Sierra) or you can use it to perform a fresh, clean install of the OS.
Provided below is the link to Apple's officially supported documentation of High Sierra's minimum hardware format of the flash drive is USB Type-A and the size of it is 16GB
I do offer faster shipping options than USPS Ground Advantage, but they do require you to pay a shipping fee. If you purchase one of these options, my handling time will be either same-day as the order, or next day, just depends on when the order is placed.
Please reach out to me if you have any further questions regarding this listing. I want you to walk away from this transaction happy and with your equipment in good, working condition.