I use this to transport audio equipment that is either heavy or so big that it's weird and awkward to carry. Mainly my Harley Benton G212 Vintage guitar cab and my multi effects unit Boss GT-100.
When you're buying this keep in mind that you might want to get some rope or one of those bike bungee cords, so you don't really have to worry about your stuff falling of the kart while on the move.
After testing out the kart with my guitar cabs I'm convinced that the kart wont break easily, since the guitar cabs are like +25kg
I don't like how you fold the kart, as you have stand on the cord that is on the bottom and pull it so the metal bends a bit and gets released from the lock. It's good in the sense that it wont open on it's own, but it's just annoying to fold and unfold it, so I personally just avoid that and try to keep it unfolded as often as possible.
I'm 165cm, so the length of the extended handle/handgrip thingy, is pretty good for me most of the time, but I'd assume that if you're much taller than that it might be a bit uncomfortable to use this.
The wheels are attached by bending a metal pin, but I didn't figure that out for a while, but when I did I realized I didn't have anything to bend the pins with, so before I got a pair pliers I just used superglue to keep the pins place... I really wish there was a more convenient way to attach and detach the wheels
Also the wheels are pretty hard so transporting fragile things like tube amplifiers might be a bit scary due to the amount of tremors that occur in every type of terrain that isn't 100% flat. I'm guessing you could make this a bit better by adding dampening or using softer wheels. I personally avoid putting my tube amp on the kart because of the hard wheels.
If you're confronted stairs or even a small ledge it's a pain to deal with as it would be with any kart like this.
Conclusion:
I'm satisfied with the product and I have already recommended it to my friends who also carry heavy music stuff. Also it's not really expensive or anything so it's not even that big of deal to buy