The tailcap assembly has always been an aluminum body with a high-impact plastic rotary dial and push-button activation switch.
The internals include a variety of metal and plastic parts.
Springs, bearings and internal housing are metal
Internal plunger is the same high-impact plastic at the dial and switch.
To date I can recall less than 5 Gladius lights we have repaired/replaced for damage to the tailcap due to impact damage. A couple of those were dropped when in Lock-Out mode where the switch has less "give".
The main thing we have had to get our arms around is consistent manufacturing (tolerarnce and assembly). Lights were having intermittent activation issues as a result. As time has rolled on there has been excellent progress in this area. Those lights that did not pass muster we have replaced/repaired as soon as possible. We have made quite a few inline changes to reduce what is called "tolerance stacking".
We now have a new U.S. partner in manufacturing, and the lights I have seen come out of there are the best I have handled/seen. They are doing an awesome job.