Packing list: 1 * T8x8 350mm lead screw 1 * T8x8 brass nut The lead of the thread is 8mm, which means that the nut will move 8mm if the nut turns one circle. The advantages of the lead screw are: Large load carrying capability Compact Large mechanical advantage Precise and accurate linear motion Smooth, quiet, and low maintenance, very suitable for 3D printer z axis. Minimal number of parts So this lead screw is very suitable for 3D printer Z axis, such as Ultimaker and Prusa i3. The screw type of this lead screw is ACME thread. ACME Threads are generally stronger than square threads due to their trapezoidal thread profile, which provides greater load-bearing capabilities.