Knock cabiner new version self defence keychain

Knuckles self defence in a carabiner keychain (desing for right hand)
this is new design remixed inspiration.
There are some versions. Last one (_Improved) with more protection for knuckles.
I want to do another version with spikes
Inspiration http://www.thingiverse.com/thing:38540 and http://www.thingiverse.com/thing:1819242

I designed for my hand (small-medium) 10cm Knuckles aprox.
20-25mm holes. For bigger hands, you can scale (2 pieces the same), be carefull that dimension of holes