Connor's left gauntlet, PVC wrapped in vinyl.
The hidden-blade is much smaller then Altair's.
It is not automatically retracted... but truth be told... The ones I've seen that do retract look like infernal machines... not exactly "hidden".
So I went with estehtics here, it pops out and locks in place. It has to be manually re-inserted though. It doesn't look like the one Connor has either, however it works... and looks okay.... So...
I looked at functionality versus esthetics and toke the middle road.
Guess it's okay!!