Well nuts are essentially a nutsert coated in rubber. These one-sided fasteners, made of a flanged rubber outside and a brass insert nut, provide a water-resistant seal so they are ideal when corrosion resistance is necessary. Well-nuts, like jacknuts, are pulled when the fastener is screwed into place, with the rubber portion collapsing on itself creating a water-resistant seal. Well-nuts, while creating a water-resistant seal, do not have as high of the pull-out strength as nutserts. Grip range is the amount of material the well-nut will be going through, not the actual length of the well-nut, which will always be longer than the grip range.