Presser feet are divided into various types. Eg Reverse Pattern Foot #1 | #1C | #1D Number only - (eg 1) machines with a max stitch width of 5.5mm. Number and C - (eg 1C) C for 'coded' and refers to the sensor that specifies the stitch width to the machine. Max stitch width 9mm. Number and D - (eg 1D) - D for 'Dual Feed' used only with machines with Dual Feed system. Max stitch length 9mm.