You might want to check with the thread manufacturer's wesite also as to the uses for each thread. I have used cotton, poly, and rayon embroidery threads.....however....in my experience rayon and cotton do not hold up as well as polythread for the quilting......you need to keep in mind how you are going to use the finished project....if you are making a wall hanging ....rayon would be great because it has a nice luster. if you are going to washing and using the project....you might want to go with cotton or poly.....(don't want to use poly in a microwave if making a potatoe holder.....). so consider the use of the project and pick your threads.....