SewLibra:
There are three layers. A paper backing, an optional fusing layer, and the woven label. You can either fuse with an iron or sew them on.
SewLibra:
I replaced my label with a Wunderlabel here on a tee. I applied it with the iron-on method under the binding. Since the fabric is a knit and the fusible layer is rather thick, it shows through on the right side. The labels themselves are not thick.
SewLibra:
Unfortuately the label peeled right off after it cooled and dried! I peeled off their fusible layer and used Stitch Witchery directly on the woven label, which worked by making a tight seal. I'll have to do that or sew them on, at least on knits.