Inner diameter 46.4 mm ,thickness 15mm .It can hold normal M42 extension tubes with 46 mm~46.3 mm.Or the 42 tube we special made for this clamp.Tools free.Tighten the tube just by hand.
1/4 inch threaded hole at the bottom.The price is only for the clamp.
Example for setting:
Setting on the quick release plate first （200mm length plate in picture）
Setting with raynox reversed .There are 4 units of 42 tubes in the picture.Sequence as below.42mm-Camera mount + 42 tube with 10mm length+50mm+50mm+50mm +raynox reversed adapter+Raynox DCR150+raynox reversed adapter +M42-M26 adapter+Mitutoyo
Work with the rail,there are 2 units of quick release clamp and 1/4 inch screw to fix on the rail platform.