They are ideal for adding some of your left over Swarovsky crystals or metals to the flower centers. All the flower centers and the outlines on the larger flowers must be done with Gold or Silver metallic threads and if you don not want to use metallic threads, then please don not buy these designs. It will ruin the designs if the flower centers are yellow, as you will also end up with certain other parts of the designs that are yellow too. That will not look nice at all.