RunYourCarWithWater - (Best Rated) Easy-to-follow instructions, great results, and an unbeatable price - [currently on sale].

Water4Gas - Intermediate difficulty instructions, above average results, and a competitive price.

Wam-a-bam - The directions are affordable with average results, but the seller does not provide technical support.

Hydrogen-Boost - Effective results, but very expensive.

HydroGen Power - We were not able to integrate this technology with any of the vehicles tested, but have heard mixed reviews.

National Vapor - $1200 cost for supplies, but there is little information about success rates.