Thumb Screw Knurled With Shoulder Head Steel Thread Size 8-32 Length 9/16 In Head Diameter 0.438 In Head Height 0.219 In Shoulder Dia 0.375 In Screw Shoulder Length 0.094 In Class 2A Rockwell Hardness B68-B71 Tensile Strength 57 000 PSI Finish Black Oxide