There is a difference.
From the AGD store:
These have the same lenght as the PE Geo/2/3 Front Frame Screw you can use too.
RT Pro Bottom Bottle Screw-Acts as Front Frame Screw:
This screw is just a shade longer than the regular front frame screw. For use with the Tac One, RT Pro, RT ULE Custom or Emag with ULE or Tac One Mainbody.
You should get those at any PE Service Center.
For the stainless bodys you would need a screw that is a little bit shorter than the screw above:
A steel mainbody uses the standard front frame screw. Be sure to choose the right part for your mainbody!