Bought this to fix a small crack on my windshield as a stupid rock flew at my car from a dump truck. I was a bit skeptical at first but after a couple of reviews and watching some YouTube instructional videos and then using the kit itself. I highly recommend it.
If you have a large crack more than 3-5cm in length. This kit won't help you. This is meant for smaller cracks and dents. You are better off going to a window repair specialist and having your glass replaced/repaired.
This kit is easy to use but I don't recommend you use the paper instructions included in the kit. Go watch an instructional YouTube video. Those videos will explain the instructions better than the paper instructions included. You should still read the paper instructions, but it is more of a summary guide. The video really shows you what you need to do and when to do it.
Overall, the crack in my windshield pretty much disappeared. There are some remnants of it. However, It is so small you barely notice it unless I point it out though. The manufacturer does warn that it cannot guarantee a 100% fix and realistically for the price you pay for it, you shouldn't expect it will.
Should I have another accident, I would buy this kit again (hopefully not though).