A simple rotating opener for easily opening keychains, 

Insert the thin part of the model into the keychain then slideA simple rotating opener for easily opening keychains, Insert the thin part of the model into the keychain then slide the keychain up and slightly lift the model to open the entrance of the keychain to allow sliding a key or anything else on. 

This model can bend keychains permanently so take that into account. 

At 0.12 layer height on a K1 SE with 25% gyroid took 25 minutes to print

Print settings - Orca
Print with 0.12mm layer height on a 0.4mm nozzle to ensure the surface is flat.
Print in the default file orientation, 
Right click the model and in the modifier selection choose a cylinder, 
Select the cylinder and set it to x: 0, y: 0 then scale it to 36mm, 36mm
In the Process → Object → Cylinder select the option for Others then set fuzzy skin to “All Walls”
Set the fuzzy skin generator mode to Combined
You can also repeat this process with a smaller cylinder to overextrude the center to get even better grip,