An assortment of expansion and well nuts from The Hillman Group. Expansion nuts, or well nuts, consist of a flanged neoprene bushing with a threaded nut embedded in the non-flanged end. As the bolt is screwed into the nut, the rubber on the other side of the hole expands and seals the bolt hole. Variants included in this assortment range from #6-32 to 3/8"-16 in fine & coarse thread sizes. Full assortments of #3318 contain twelve (12) refills comprised of Hillman item numbers #3319 - #3330.