24Piece, 3/8″ Grommet Kit, Contains Brass Grommets With Hole Cutter & Hardwood Backer Block, Hardened Mandrel & Anvil, Setting Tool Has Knurled Body For Greater Comfort & Safety, Sizes Individually Marked On Setting Tool & Coded With Lines On Anvil, Setting Tool & Cutter Are Heat Treated For Long Life, Black Oxide Plating Prevents Rust.