Now Im not worried about taking my comandante on the road and breaking the glass bean jar. This is a solid swap for traveling.

Exactly what you'd expect. Nice for fun pops of colour to your brew bar.

I prefer the polymer jar when screwed into my MK3 and used as a catch cup. It's lighter and screws in tighter so I don't feel like it could unscrew by itself while i'm grinding. Only downside is when used as bean storage jar - I can faintly smell the coffee inside the jar even when closed tightly, suggesting it's not airtight without the white paper seal that the glass jars had. When storing ground coffee when going out, I get a strong whiff of coffee even from my bag under my desk.

I can't speak for the included glass jar with the Mk 4 Comandante, but this jar is much better than the Mk 3 Comandante's glass jar.
There is no inside lip below the threads which grounds can get caught on and the polymer jar also holds less static so coffee grounds, especially fine ones, are much less likely to stick.

Love these for pre dosed coffee on the go. I use these to grind at home and have pre dosed coffee to take to the office for my pour overs. I love that they are not glass, and the variety of colours.