I use C&C 100 % egyptian cotton thread in all my machines which include the Diamond, SE, Sapphire, Pfaff 4.0 and all my Singers and never had a problem...I know Viking and Pfaff recommend "G" for their machines..I happen not to like "G" thread. The "G" thread makes a fat thread stitch on my machines... Funny, My embroidery machines don't like Sulky embroidery thread.