Zinc plated Form C washers are slightly wider on the outside diameter than a form A or B washer. They are generally better for heavy duty applications as the load can be spread over a wider area.
| BOLT SIZE | INTERNAL DIAMETER (MM) | EXTERNAL DIAMETER (MM) | THICKNESS (MM) | 
|---|---|---|---|
| M4 | 4.3 | 10 | 0.8 | 
| M5 | 5.3 | 12.5 | 1 | 
| M6 | 6.4 | 14 | 1.6 | 
| M8 | 8.4 | 21 | 1.6 | 
| M10 | 10.5 | 24 | 2 | 
| M12 | 13 | 28 | 2.5 | 
| M14 | 15 | 30 | 2.5 | 
| M16 | 17 | 34 | 3 | 
| M18 | 19 | 37 | 3 | 
| M20 | 21 | 39 | 3 | 
| M22 | 23 | 44 | 3 | 
| M24 | 25 | 50 | 4 | 
| M27 | 28 | 56 | 4 | 
| M30 | 31 | 60 | 4 | 
| M33 | 34 | 66 | 5 | 
| M36 | 37 | 72 | 5 | 
| M39 | 40 | 77 | 6 | 
 
                     
                    



 
     
     
     
     
     
     
     
     
    