Power Fasteners Combo hollow wall anchor spring wing toggle bolt features ANSI B18.6.3 carbon steel construction with zinc-plated finish for superior corrosion resistance. This UNC bolt has thread of size 3/8 Inch and 16 TPI. It measures 4 Inch x 3/8 Inch Dia. Round headed bolt has slotted/Phillips driver. It has drill size of 7/8 Inch. This bolt is perfect for block, wallboard and other hollow base materials.