Seamless Follow Focus Gear for the Sigma 18-35mm f/1.8 DC HSM Art Lens Custom fit to this particular lens Access to all 360 of gear with no clumsy straps or screws to keep firmly in place Can be left on lens permanently or easily removed if needed Lifetime warranty, guaranteed to fit or we will make corrections absolutely free Best return policy - If you don't like the gear, we'll fully refund it if you're not satisfied