Thumb Screw Knurled With Shoulder Head Steel Thread Size 5/16-18 Length 1 In Head Diameter 1.250 In Head Height 0.250 In Shoulder Dia 0.625 In Screw Shoulder Length 0.500 In Class 2A Rockwell Hardness B68-B71 Tensile Strength 57 000 PSI Finish Black Oxide