For USB printing, there are plastic, pvc, metal and leather USB printing, they all can be printed by UV printer with UV ink directly
USB printing, usually they are printed grouply, it need a tray for fixing it. if you have many different size of USB, it is also ok to use a kind of tape instead of the tray, main function is to fix the printing materials.
For USB printing, if your USB is light color, it is ok to print color ink ( C M Y K ) only, if your USB is dark color, it need to print white ink first, then color ink, also it support printing with embossment.
USB printed by uv printer, which will not fade from color and it is scratchproof.