管材横向划黑线的一端壁厚均匀性较好。从该部位出发，一直到黑色记号处（靠近另一端端头），为建议使用部分，长度约55cm。剩余部分供切割支架时夹持用，约20cm。

The tube has a better wall thickness uniformity at one end of the horizontal black line. Starting from this part, all the way to the black mark (near the other end) is the recommended part, about 55 cm in length. The remaining part is for clamping when cutting the stent, about 20 cm.