Material:3D Printer belt tensioner made of good quality cold rolled sheet material, Surface oxidation treatment,Sturdy, fine workmanship Install:Already assembled,you don't need to assemble it by yourself,No need to change the original belt length,direct installation and ready to use Function:you can adjust the belt freedom, more better than original Widely Used: Widely used for Ender-3 upgrades Series Package Content:1 Kit 2020 Profile X-axis Synchronous Belt ,1 Kit 4040 Profile Y-axis Synchronous Belt Stretch Straighten Tensioner