An AN16 flare union adapter, male at both ends, for coupling two AN16 female hose ends or ports. AN16 lines carry the highest volumes on a build — scavenge, vent and large cooler circuits — and hose at this diameter is awkward to route in one length, so a union that lets you build the run in two manageable sections is genuinely useful. It also creates a service break point for pulling a tank, cooler or pump without dismantling the whole circuit. Both ends seal on the 37° AN flare cone, metal to metal, with no sealant required. Given the weight and stiffness of AN16 hose, clamp the hose either side of the union so no bending load is carried through the joint, and tighten to snug plus a small nip only.