This prepreg composite material doesn't cure like you think. Prepreg (pre-impregnated) means the fabric already has resin in it. Epoxy, vinylester, or polyester. This system uses UV initiators IN the resin, so it only cures when exposed to UV light. You can lay up your part for 2-3 hours without it going off. Then throw it outside for 5 minutes. Hard. Done. The long working time means you're NOT racing the clock during layup, and UV activation gives you total control over when it cures. Perfect