It is the same as the original Lava Tubes. Basically, it is a metal tube. There seems to be a top cap (plastic/delrin), but I have not been able to spin it. The bottom cap(plastic/delrin) unscrews to reveal the battery bay that holds one 18650 Battery (standard size LT). Even though the bottom cap is a type of plastic, it holds a metal thread and the spring, my guess would be that the plastic cap is glued to the actual metal cap? The battery is easy to change, unscrew the bottom cap dump old batt and put in the new one. I have put 4-5ml through it so far at 4.5 Volts and the battery still shows 3 of 5 Bars for life yet. Yes, 1 Batt in the Tube and 1 Batt on the Charger. I opted for 2 extra Batts for a total of 4 Batts as the Vmod and Old Goat were both 14500 and the LT was 18650.
I have not dropped it yet, and do not plan to. I do not think it is as durable as an Ego, but you are comparing a closed device to a tube that holds a battery. Also, I use full size cones over my Cartos on my Egos if I am not using a Tank, so it may feel sturdier because of that.
I have been looking at the Stardusts for a bit now, but was hesitant to try on low voltage of my mods at the time. Trying to figure out where I want to get my next Juice order from, so I will pick somewhere that also sells the Vision Stardusts in the non Ego cone thread cover version.