1. M54x0.75 extension cylinder. 2. The Extension Ring has length of 4mm,5mm,6mm,7mm,8mm,9mm. 3. Scope of application: back of photography 4. Pitch: 0.75.<br><br>Length of internal thread is as follows: 4mm-female thread length is 3mm 5mm-female thread length is 4mm 6mm-female thread length is 4.5mm 7mm-female thread length is 5.5mm 8mm-female thread length is 6mm 9mm-female thread length is 7mm Colour:As Shown Material:Aluminum Alloy<br><br>Package Contents: 1 * 4/5/6/7/8/9mm kits Extension Tube<br><br>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.