An AN10 flare union adapter, male on both ends, used to couple two AN10 female hose ends or female ports back to back. The everyday reasons to reach for one are splitting a long run into two shorter, easier-to-route hoses, joining a hard line to a flexible section, or creating a break point at a bulkhead or firewall so a component can be removed without draining the whole system. Both ends carry the standard 37° AN flare seat, so the metal-to-metal cone does the sealing and no tape or liquid sealant belongs anywhere near it. AN10 suits high-volume fuel feeds, oil cooler and dry-sump circuits. Tighten to snug plus a small nip, and support the hose either side so the union is not carrying weight.