The unwinder is designed for unwinding the labels as the printer feeds it. The method of unwinding labels externally offers advantages in case you want to have control of the label roll or you want to use bigger label rolls than the printer can contain.
The Unwinder(UW) models are made in 3 different models. Different models can take label width size 65mm, 110mm or 180mm, and label roll diameter size 240mm or 360mm. If you are looking for a small or medium size Unwinder you should look at UW2S, UW4S or UW6S depending on the width of your labels. For more "Heavy duty" operations you should consider the Heavy duty Unwinder UW4L which can take roll diameter of 240 or 360mm.