Purl threads and Bullion threads are very similar except that the Purls are smaller in diameter and more suited to smaller projects. Bullion threads are large and more suitable for big goldwork embroidery projects such as alter cloths and pulpit paraments which are seen from a distance and need to be visible. Purls and Bullions are very fine wire threads in a tubular shape. They are hollow, soft and flexible metal tubes. The tube is cut into pieces and sewn down like a bead.