These two rings will set the raynox DCR 150 reversed as below.
How to build a tubelens with raynox DCR 150 or 250.Please notice this link only contain two adapter rings.
It will be better to put some black paper or some material can absorb internal reflection in M42 tube.
Please notice:this link only contain two adapter rings.The objective lens and M42 tube are not included.
There is a test about DCR150 reversed and normal setting comparison.The objective lens we use is Mitutoyo APO 5X with DCR150 with a APS-C camera.
Please download the file,zoom 100% compare the corner especially,and you will find REVERSED is BETTER than normal setting.