The soutache from the BeadSmith comes in both Rayon and Polyester
Rayon is a semi-natural fibre - it is essentially re-processed cotton. Has more sheen and a muted colour palette
Polyester is an entirely synthetic fibre so it is slightly duller but has brighter colours.
The entire line of BeadSmith soutache was designed by a textile Jewellery artist so tremendous attention has been paid to consistency of width, thickness and drape. This ensures the rayon and Polyester braid can be used together successfully.
All care has been taken with the photos but there may be some colour variance due to looking at colours on your screen.