12mm Spindle Clamp

This is a clamp I invented to hold parts in place on spindles. For example I use 2 of them to keep my filament spool in place. My aim was to create a clamp that could be placed and locked single handed, and provides reasonable holding force. The result seems to do the trick, has no moving parts, and requires no assembly.
The outer ring acts as a spring which when squeezed spreads the inner half rings apart.
PLA works ok but does take on a bit of a set and so relaxes a little over time. A