Amazon.com: Flex Seal, 14 oz, Clear, Stop Leaks Instantly, Transparent Waterproof Rubber Spray On Sealant Coating, Perfe vs Waterproofing Wax for Leather: which is safer?

Where these two actually differ

• We flag Volatile organic compounds (VOCs) from spray application, Isocyanates or other respiratory sensitizers, Surface leachates into water (if substrate contacts food or drinking water) and Coating adhesion loss and microparticle shedding over time on the Flex Seal and not on the Nikwax.
• We flag Respiratory irritation or fume inhalation during application and PFAS in water repellency treatment on the Nikwax and not on the Flex Seal.
• The Flex Seal is rubber spray coating, composition unspecified where the Nikwax is wax-based waterproofing, which is most of the difference in these two grades.
• The gap is 25 points, wide enough that this is not a close call, and the Nikwax is the one to buy.
• We are less certain about the Flex Seal grade, at 35% confidence against 78%, because it discloses less.