I finished assembling the gripper for the RR1 rev.2. Most notably each finger of this new gripper has two parts connected by a joint, so it is much more dexterous and can grip an object much better than the fixed gripper in RR1 rev. 1. I also improved friction, the inner surface of the gripper has many small inti-slip pads (rubber bands as in rev.1 are no longer necessary). I did a test and, for example, the gripper is perfect for holding a glass or a can. The tip of the gripper when closed can operate as tweezers.
As for the material, it is a combination of PETG, flexible filament and polycarbonate with carbon fiber. Plus some linear bearings many screws and bolts.