Underwear telescopic buckle is also called bra telescopic buckle, mainly to avoid the situation that the cup is suitable and the bottom circumference is too small and too tight. The size of the bra base is generally an integer of 70, 75, 80, 85, but in fact, everyone's base size is not an integer, usually it is 73, 79, 86, 9 1, so the bra back buckle is designed with three gears to adjust the tightness of the base, but in many cases it cannot be adjusted to a more suitable position, which leads to.