Outdoor Grommet Set: Gearbox GX1, GB3K, M40, GBX1 & GB250Gearbox Outdoor Grommet & Bumper Set. The indoor bumpers was standard on all models GB3K & prior, while providing a slightly lighter alternative for the GX1 Series. The outdoor grommet set is standard on the new GX1 Series, and provide a upgrade to a greater level of protection for all earlier models. Suitable for the following models: Gearbox GX1 Series All Models. Gearbox GB3K Series All Models. Gearbox M40 Series All Models. Gearbox GBX1 Series All