The model of the snap button is determined by the size of the next three pieces, and the commonly used models are 655, 633, and 831.
The three BCD pieces are generally referred to as "the next three pieces". The surface of the snap button (A piece) can be changed at will, but the next three pieces generally have their general rules.
The lower three pieces of the 655 model can be matched with surface buckles with a diameter of less than 10mm;
The lower three pieces of the 633 model can be matched with a face buckle with a diameter of 11-15mm;
The lower three pieces of the 831 model can be matched with surface buckles with a diameter of more than 15mm
