Hi! I designed a hook prosthetic arm. 

Check the file here: HProsthetic

BOM: 
6 x Socket Head Screw M3 x 0.5 mm Thread Size, 20 mm Long
1 x Socket Head Screw M3 x 0.5 mm Thread Size, 30 mm Long

7 x Hex Nut M3 x 0.5 mm Thread Size
2-3 rubber bands
Elastic ribbon
PTFE Nylon Tube
Bike brake cable
EVA sheet layers to glue inside the socket
If you do not want to print the TPU, you can add the non-slip material to the finger manually. 

I would appreciate feedback to further improve the design so that those who need it can benefit.

This design is not included in memberships; please let me know if any modifications are required.

I used this strap adjustable buckle :