This is another part of my Predator gear. This time the Smart Disc. It is retractable (as in the movie), though do not expect anything fancy - it only extends.

Also, it has large holes for fingers but to those holes I designed inserts so that it could be tailored to specific finger diameter. (Thus you only need to adjust the models of the inserts and not the disc parts themselves).

Note: I will be honest, the “unfolding” of the disk is not really smooth…. :(