Needle Bar Height Thickness Gauge. Must also have part number 003787G02.
Use with: 104DNH, 134D, 204D, 234, 234D, 303, 334D, 434, 434D, 504D,534D, 634D, 644D, 734D, 744D, HF3434D, 7034D, 9002D, 9102D