I have several of them

they're very sturdy, at least the slammed 510 tips are. They fit really firmly in the tanks I use them in, except the starre tank for some reason. I really like mine, they improved the flavor a lot for me and are easy to clean. I much prefer them to metal or glass personally, they don't get hot from chain vaping or cold between uses.
This is just my opinion compared to the metal and glass wide bore tips I've used, these are much wider and sit flush with the top of my herakles tanks. All in all a great company and they ship really quickly, but it can be hard to find them in stock in certain colors.