The metal measures 20 1/2 inches

Hello there!

Thank you for reaching out to us. We're happy to help with this. What you have here isn't something that's apart of our stock catalog but we can still assist via custom order. However, the metal channel should measure 20-5/8" long. Can you double-check that for us? Can we also see a photo of the top fitting? Custom orders are nonrefundable so we just want to be thorough.