Mine was (actually is) metal hard lines out of the trans, to about 18" or so away from b&m super cooler, formed a bubble at the end of each line to create a barb, hose clamped reinforced rubber trans cooler hose, to NPT barb fittings on the cooler, clamped there too.
That's my setup now, other than my trans-spec rubber hoses are closer to 36" long. Never had issues, but gonna upgrade for peace of mind.
2021 Challenger 6.4L Scat Pack 1320 100% stock: 1.680, 11.894 at 113.75 (DA 175 ft) weight reduction, wheels, tires, Hellcat air box: 1.661, 11.686 at 115.97 (DA 710 ft)
1973 Challenger 452 ci street/strip [2008] pump gas, DOT radials: 1.454, 10.523 at 126.44 (DA 514 ft)
