Review (4/5): Works well for Retr0bright
Like several others, I purchased this to make Retr0bright for ABS plastic. It works very well for that purpose, but be sure to wear gloves so that you don't burn yourself. Just simply bathe it in UV light and let it sit for a few days to brighten the plastic.
On another note, if you have a Sally's Beauty near you, I'd recommend buying from the physical store. You can get a full gallon for about $12.