The hollow square hole of the titanium alloy adopts the installation tool of the integral middle shaft, and the value of the body exceeds the axis of the ordinary square hole. The middle shaft adopts multiple waterproof and has high durability. The center of the titanium alloy shaft is fully hollowed out, and the center shaft within 800 is a center shaft with a hollow axis of titanium alloy. The new titanium alloy shaft, titanium alloy hollow shaft +7075 aluminum alloy shaft bowl structure, the shaft bowl locking method is the same body shaft, convenient and more beautiful. The rubber ring is waterproof before and after the bearing, no need to worry about the water inlet problem. the middle shaft is equipped with aluminum alloy tube sleeve, which has better waterproof performance and better texture. Colour: Black Material: titanium alloy Package Contents: 1* square taper bottom bracket for brompton Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.