This is a proprietary blend designed to improve the already excellent moisture exclusion effectiveness of WEST SYSTEM® epoxy still further. At the same time 422 Barrier Coat Additive™ increases the abrasion resistance and this combination makes it an excellent additive to use in order to prevent gelcoat blistering on boats. It’s used simply by adding 20-25% by weight to the mixed epoxy. If you need larger quantities kindly contact us.