Gantry plate is made from Aluminum material, black treatment, wheels shell are made from POM Compatible with 2040 and 4040 V-Slot aluminum profiles or Linear Rail Our POM wheels are machined with high precision, working smoother, and less friction size: 87x88x3mm, 6holes is dia 7.2mm, 37holes is 5.1mm dia. It is assembed with 6 wheels, very easy to install it Package: 1set assembled gantry plate kit