The length of the extension ring is 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 15mm, 20mm
Outer diameter: 60mm
Spacing: 0.75
External thread length: 3mm
Color: Black
Origin: Chinese Mainland
4mm internal thread length is 3mm
5mm internal thread length is 4mm
6mm internal thread length is 4.5mm
The length of the 7mm internal thread is 5.5mm
8mm internal thread length is 6mm
9mm internal thread length is 7mm
10-20mm internal thread length is 8mm