A-paper is the film on which the motif is printed. The toner adheres perfectly to the specially coated film and does not contaminate the printer.
The B-paper produces an additional opacity, which is necessary for the luminosity of the colours on dark textiles. The opaque coating on the B-paper combines only with the toner on the A-paper.
Thus you can process even very finely detailed designs without problems.
*Check for color intensity without white toner.