High speed viscoelastic jets enter a quiescent bath of water through a nozzle with 514 µm diameter. Left: aqueous solution of 326 ppm polyethylene oxide (PEO) with Mw = 1,000,000 g/mol, right: aqueous solution of 10 ppm PEO with Mw = 8,000,000 g/mol. For both jets, Weissenberg number is Wi = 3 and Reynolds number is Re = 600. The jet with lower finite extensibility polymer transitions to turbulence via a helical instability, the jet with higher finite extensibility polymer transitions to turbulence through a unique inertio-elastic instability that generates filaments of dilute polymer solution around the core of the jet. The turbulent structures, consisting of elongated coherent structures in the streamwise direction, are smaller in the jet with lower polymer extensibility compared to the jet with higher polymer extensibility.