A thermal transfer ribbon has to suit the label it is printing onto. Get the pairing wrong and the print either smudges under a thumbnail or never adheres properly in the first place. There are three grades.
Wax
The cheapest and most common. Prints onto matt and semi-gloss paper labels at lower head temperatures, which is also gentler on the print head. It scratches fairly easily and does not like solvents or oils.
Right for: general warehouse and shipping labels, retail shelf labels, anything on paper that lives indoors.
Wax-resin
The middle grade and the safest default if you are not certain. Handles coated paper and some synthetics, gives a sharper edge than wax, and stands up to moderate rubbing. Good for small barcodes and fine text where wax would look soft.
Right for: product labels, jewellery tags, labels that get handled repeatedly, higher-density barcodes.
Resin
The most durable and the most expensive. Made for synthetic stock - polyester, polypropylene, vinyl - and survives heat, solvents, oils and sustained abrasion. It needs a higher head temperature, so it works the print head harder.
Right for: asset tags, chemical drum labels, electrical and automotive parts, laboratory labelling, anything that must last years.
Two practical notes
First, ribbon width should be slightly wider than your label, never narrower. A ribbon narrower than the label lets the exposed edge of the print head run dry against the media, which wears it unevenly and will eventually cost you a print head.
Second, check ink side in or out before ordering. Printers differ, and a ribbon wound the wrong way will not transfer at all.