Thread & Fit: UNC coarse 5/16"-18 thread,External Hex drive. Pairs with standard 5/16"-18 bolts, screws, and studs. 5/16"-18 UNC (Coarse) 1/2" (0.500") 0.577" (approx.). 17/64" (0.266") Plain / Uncoated Stainless.
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