Can give E6B2 OVW TRD encoder, such as can be fixed on the market through 20 type, diameter, 38, 40 of the encoder Optical axis comes with M8 screw holes, you can add the length of the shaft according to your actual use Usage: Industrial DIY Supplies: Metalworking Standard or Nonstandard: Nonstandard Use with rotary encoder to measure velocity and position It have high resolution Structure: Single-side Bracket Colour: Silver & Green Material: Aluminum alloy + polyurethane Size: Overall Size: 14x9.4x4.8cm /5.51x3.70x1.88 Inch( L x W x H), Inner hole size: 6mm, Perimeter: 200mm Package Contents: 4 x Encoder Mounting Bracket 12 x fixing screws 8 x locking screw 4 x Encoder wheel 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.