They're made by GSO, and therefore I assume the same optics in all the GSO dobs available from Bintel, Andrews and others.
I guess you'd conclude from that, "great for the price"
Many of us with GSO optics are doing high resolution planetary imaging, and others are doing deep space imaging as well. As long as it's collimated, it performs very well for something that's mass-produced.
Sorry I can't give anything more technical