There is a difference between a Material (MT5 or MC6) and a MAT Pose (PZ2).  Materials are new to Poser 5 and are directly connected to the newer Material Room/Shader Node system added then.  MAT Pose files are the old, but still very much employed, way of setting up materials.  They are two different file formats and non-interchangeable.  An RSR will not help make the MT5 file work in the Pose library.

What you'll need to do is convert the Material into a MAT Pose.  This may be possible by loading the Material onto the target Poser figure/prop and then adding the pose to the Pose library ('+' at bottom of Library).  If the materials are included with the pose, you can edit out other information to make it a MAT Pose.  At worst, you can save the Figure or Prop to the library and edit the file down to a MAT Pose.  It's a cumbersome process, but Poser really doesn't offer the tools to make things like MAT Poses or MOR Poses (morphs only), these being more or less exploits not official formats.

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

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