I think the idea is that the Growler is a play on words because a Growler is a unit of alcohol bigger than a pint.

According to Fallman Tech

"It all began when the Onehweel Pint was released, the guys behind the Float life started to make a wish list for the perfect Onewheel. What came out of this was the upgrade kit of the Onewheel XR making it into the Growler. They describe it as a larger, beefier, Pint. Retaining the XR footpad real estate, while incorporating the agile, nimble, manoeuvrable, responsiveness of the Pint."

Nowadays there are several different Onewheel Growler builds, you can check those out here.

Should you buy the Onewheel Growler?

Scot Mendenhall had really great things to say about it:

And the reviews on reddit are pretty good.

And now my take

I don't have a Onewheel XR but I think if I did and I knew that the supply and support of those boards was going to be declining, this is exactly what I would do.

It makes sense if you have an XR that's out of warranty but still works to continue to get support via 3rd party vendors like TFL, so for me, the Growler is a win and a clever idea.

If you have an extra couple bucks to spare and an old XR, give it a try and tell me what you think in the comments.