Smooth Running - Upgrade Single Z- structure to a dual Z- structure, avoiding backlog of filament thoroughly, which improves stability of 3D printing. Easy Leveling - Both ends of the X are raised and lowered synchronously, which reduces difficulty and frequency of bed leveling obviously. Increased Accuracy - Compared with original structure, dual Z- kit reduces the layer ripple caused by Z- vibration, increasing the printing performance of 3D printer. Stable Performance - Compared with Closed Timing Belt, this 3D printer parts set still retains the design of stepper motor to screw rod smooth operation. Easy Assemble - No need to modify or weld the machine, no need to replace motherboard, this 3D printer accessories kit comes with instructions, could be assemble quickly. Colour: silver + black Material: plastic + stainless steel Package Contents: 2 x 3D printer Z upgrade kit 2 x English manual Only the above package content, other products are not included. Note: Light reflection 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.