This accessory spool cap is used to stabilize spools of thread on your spool pin. This 35mm spool cap is for use with the Husqvarna Viking Designer Diamond Deluxe, Designer Diamond, Designer Ruby, Designer Topaz 20 & 30, Tribute 140C, Sapphire 875Q, 870, 855, 850, 835, 830,Designer SE, Designer I, Designer II, Quilt Designer, Quilt Designer II, Platinum 955E, 950E, Plus, 775, 770, 755Q, 750Q, 735, 730, 715.~