MHD simulation of a magnetised triangular jet in type II spicule conditions. The half-width of the jet is 100 km and the total length of the simulated jet is about 7 mm. The initial transverse perturbation has an amplitude of ∼10 km s⁻¹ (corresponding to 10% of the flow speed at the jet centre) and a spatial scale of around 600 km. We show the mass density ρ (left panels), the flow velocity V_z (middle panels), and the z-component of the magnetic field B_z (right panels) at consecutive snapshots, each 15 s apart (upper panels correspond to the initial set up). A pronounced kink develops around 30 s after initial perturbation and turns into an instability after ≈45 s. Corresponding movies can be found online.