Commonly used in fuel pump applications, this brass adapter has 1/4" Male NPT threads on one end and a 5/8-18 thread female inverted flare connection on the other end to accept 3/8 inverted flare tubing. Always use Teflon thread tape or Teflon thread paste on tapered pipe threads. Do not over tighten tapered pipe fittings as they can crack the housing they thread into.