All ORFS plugs are designed with UNF male thread and flat face end with O- ring seal, The caps are designed with UNF female threads body and plug inset, which fixed by O-ring, This Hydraulic O-ring seal plug and cap set includes 6 most common UNF threads size, #4 for 9/16''-18, #6 for 11/16''-16, #8 for 13/16''-16, #10 for 1''-14, #12 for 1-3/16''-12, #16 for 1/7/16''-12. 72pcs totally, 12pcs #4-plugs, 12pcs #4-caps, 10pcs #6-plugs, 10pcs #6-caps, 6pcs #8-plugs, 6pcs #8-caps, 4pcs #10-plugs, 4pcs #10-caps, 2pcs #12-plugs, 2pcs #12-caps, 2pcs #16-plugs, 2pcs #16-caps. 72pcs totally.