DMC-Petra Crochet Cotton Thread. These balls of highly mercerized cotton are lustrous non-divisible and made of 100% cotton. Perfect for cross stitching needlepoint and embroidery on a wide variety of fabrics when a rich raised pattern is desired and for the finest of crocheted lace. Size: 5. Length: 306yd (280m). Comes in a variety of colors. Each sold separately. Machine washable dry clean safe ironing safe do not bleach. Dry cleaner safe with P solvents. Imported.