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METRIC WRENCH SIZING CHART

Nominal Opening of Proto Wrenches or Sockets in Millimeters to Fit Standard Bolt Heads and Screw Heads

Locate thread diameter of bolt or screw in left column. Then move across to box which has proper identification of bolt or screw at top of vertical column. The size in this particular box is the nominal opening size in inches of the PROTO wrench and sockets that will fit.

WRENCH OR SOCKET SIZE ACROSS FLATS
HEX BOLTS
HEAVY HEX BOLTS
HEAVY HEX STRUCTURAL BOLTS
 
Use wrench or socket size shown below?
3.20
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4.00
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5.00
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5.50
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6.00
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7.00
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8.00
M5 x 0.8
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10.00
M6 x 1
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13.00
M8 x 1.25
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15.00
M10 x 1.5
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16.00
M10 x 1.5
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18.00
M12 x 1.75
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21.00
M14 x 2
M12 x 1.75
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24.00
M16 x 2
M14 x 2
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27.00
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M16 x 2
M16 x 2
30.00
M20 x 2.5
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34.00
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M20 x 2.5
M20 x 2.5
36.00
M24 x 3
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M22 x 2.5
41.00
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M24 x 3
M24 x 3
46.00
M30 x 3.5
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M27 x 3
50.00
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M30 x 3.5
M30 x 3.5
55.00
M36 x 4
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60.00
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M36 x 4
M36 x 4
65.00
M42 x 4.5
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70.00
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75.00
M48 x 5
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80.00
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85.00
M56 x 5.5
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90.00
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95.00
M64 x 6
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100.00
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105.00
M72 x 6
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110.00
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115.00
M80 x 6
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120.00
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130.00
M90 x 6
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135.00
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145.00
M100 x 6
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150.00
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