The zinc alloy double wheels, the thickened zinc alloy frame has excellent corrosion resistance, and the sturdy frame is not easy to break and crack.The cylinder is used as a rolling body, which is evenly stressed and quiet; it stays smooth when rollingThe thickened zinc alloy frame has excellent corrosion resistance, and the sturdy frame is not easy to break and crack.opening. : 4mm/0.16"; Roll Size (per roll): 12 x 8mm/0.64" x 0.31" (D*D)Overall Dimensions: 68.5 x 16 x 15mm/2.7" x 0.64" x 0.59" (L*W*H); Weight: 59gPackage Contents: 1 window pulley.Designed with two silver metal rollers for easy use, it's an ideal accessory for doors, windows and more.Note: The data are all manual measurement, please allow 1 - 3cm error, due to the difference in light and display, there will be a certain color difference, depending on the physical object receipt Delivery quantity: (according to the main image)