Industrial encoder accessories, encoder wheels, and encoder meter wheels are all components used in conjunction with encoders to help measure the position, speed, or direction of a rotating shaft or linear motion. Encoder wheels are typically made of aluminum or plastic and have evenly spaced slots or holes around their circumference. As the wheel rotates, an optical or magnetic sensor detects changes in the pattern of slots or holes and uses this information to calculate the shaft's rotation angle or linear travel distance. Encoder meter wheels are similar to encoder wheels, but they have a tire or tread that makes contact with the being measured. This type of encoder is commonly used for measuring conveyor belt speed or other linear movements. [Material] Made of aluminum and rubber, not easy to wear, and lasting performance. It's a great substitute for your product. Size parameters thickness: 12mm Perimeter: 300mm/11.8 inch Bore Diameter: 6mm/0.24 inch Colour:black Material:aluminum+rubber Package Contents: 2 x Encoder Wheel 2 x Wrench 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.