Two types of 303 and several types of waterproofer
Original 303 got its name from batch "303" on an anti-oxidant/UV blocker. This was the first of this type of product and later copied by many, including West Marine's own brand.303 cleverly got manufacturer's endorsements however.This stuff does work as it should although not much documentation scientifically in the early days, there was plenty of anectotal stuff. 303 put out a great flyer "why are tires black etc" whose only inaccuracies included treating all silicoanes as certain silicone oils, ignoring that the mold release for all tires, gelcoat etc is silane based. Saying "silicones" is like saying "carbon-based" there is a huge variety and usefulness.There are several commercial waterproofers on the market - many used for the commercial awning business. The best (most effective, made by Astrup) are solvent based. Others use water -based emulsions, All use silicones for water repellency. This is a balancing act of using non-yellowing constituents and minimizing dirt attraction.All "home use" fabric sealants like this are water emulsions. In fact, even IG's Silkenseal will seal sail covers etc, although non designed for this purpose.303 has a fine reputation, built on its UV protection and has resisted influx of competing products very well.with both the UV protectant and the fabric protectant it is worth doing a small test area if you plan to use on WHITE fabrics.Another boring diatribe from yours truly!