Features: Brand new and high quality V-shaped wheel can perfectly adapt to the inverted track, and can reduce vibration, suitable for V-shaped groove track. Material: Made of high quality standard 45 # steel with galvanized, The thickness of bracket is 11 gauge (3mm). These v-groove wheels are precisely machined, solid construct, consistent quality, and very smooth rolling, corrosion resistant. Strong Load Capacity: Each heavy duty caster allow load 440 lbs capacity, All four casters easy to carry up to 2200 lbs. Smooth Rolling: Each wheel built in double 6000RS chrome steel seal ball bearings for higher resistance and durability. These v-groove wheels on an inverted v-track have much less rolling friction and have changed the roof rolling off from a hard job to an easy job. Applications: Fit to inverted 90 degree angle v-track, heavy duty rolling door, sliding gate, industrial machines rail, wire rope rail device, containers racks, sawmill, dog fence and more. Specifications: Material: Steel Base plate diameter:1.2 Inch-- 56mmx30mm A single load-bearing capacity:1.2 inch--200kg (440 pounds) Package Includes: 4Pcs x Sliding Door Pulley note: No retail package. Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!