What's the use of traditional bow and arrow pads? Why is there a Manchu bow and not a Han bow?

After entering the Tang Dynasty, China Bow had some changes. On the Gaochangjiao Bow, the only existing unearthed object of the Tang Dynasty, a ring-shaped gadget, the so-called "string pad", appeared at the position where the upper and lower bow strings meet the bow tip. This little invention should be said to be very practical. We know that the bowstring will bounce back when the archer releases the arrow, because of the posture problem. Anyone who hits the arm with the bowstring and bounces back knows how painful it is. Because the bowstring has a strong rebound force, under the condition of continuous arrow release, the bowstring collides with the bow arm repeatedly, which is easy to reduce the life of the bowstring or even directly break it. With the string pad, the bowstring directly passes through the string pad and is fixed, so that it will be buffered by the string pad when it bounces back, and the collision force will be greatly reduced, thus greatly prolonging the life of the bowstring and reducing wrist fatigue caused by repeated collision between the bowstring and the bow arm. Because this gadget is so practical, since the Tang Dynasty, almost all the bows of nomadic people in the Central Plains and the north have been fitted with string pads.