Brand new concave step chuck to hold barrels, wheels, etc.

The thread is metric size M7 x 0.75mm Very fine quality. You can select the size as following 

No. 1  step chuck from diam. 7.0, 9.0, 11.0, 13.0, 15.0, 17.0, 19.0, 21.0, 23.0mm

No. 2  step chuck from diam. 6.6, 8.6, 10.6, 12.6, 14.6, 16.6, 18.6, 20.6, 22.6mm 

No. 3  step chuck from diam. 6.2, 8.2, 10.2, 12.2, 14.2, 16.2, 18.2, 20.2, 22.2mm 

No. 4  step chuck from diam. 5.8, 7.8,  9.8,  11.8, 13.8, 15.8, 17.8, 19.8, 21.8mm