SAE J517 standard specified hydraulic hose assembly length measurement such as
Straight connectors (except O-ring face seal)
Female swivel elbow connectors
O-ring face seal connectors
Unless otherwise specified, assembly length shall be the overall length measured from the extreme end of one connector to the extreme end of the other, except for O-ring face seal type connectors which shall be measured from the sealing face. Where elbow connectors are used, measurement shall be to the center line of the sealing surface of the elbow end (The sealing surface of female flared elbow connectors shall be the centerline of the outer end of the cone seat).