M16 - Outer:30.0mm Inner:16.9mm Thickness:3.0mm. M8 - Outer:16.9mm Inner:8.5mm Thickness:1.6mm. M12 - Outer:23.9mm Inner:13.0mm Thickness:2.5mm. M10 - Outer:20.9mm Inner:10.5mm Thickness:2.0mm. M4 - Outer:9mm Inner:4.4mm Thickness:0.8mm.
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