I dunno, it's an additive that enters the coolant stream and seems to be similar to Bar's Stop-Leak. While it may be fine for small leaks, I personally doubt it will do the job for a cracked head or really bad head gasket.
I would hesitate to drop $100 on it, without first checking the ride with a trusted mechanic.
__________________ Attack Pig {aka Tam}
**Disclaimer** An honest opinion is not always appreciated by the recipient.
Attack Pig {aka Tam} 
