Oatey® No. 5 Paste Flux is a petrolatum-based flux designed to provide superior wetting properties for better solder flow. It can be used with most soft solders. 100% lead free, No. 5 Paste Flux is NSF listed for potable water applications. Its formula resists turning copper piping green and is excellent for large diameter copper pipe applications. Made in the USA. Oatey products have earned the trust of plumbing professional for over 100 years.