Copper Form B washer, identical diameter to Form A washers, but thinner. Commonly used in plumbing applications and are useful in construction and industrial machinery.
| BOLT SIZE | INTERNAL DIAMETER (MM) | EXTERNAL DIAMETER (MM) | THICKNESS (MM) | 
|---|---|---|---|
| M3 | 3.2 | 7 | |
| M4 | 4.3 | 9 | |
| M5 | 5.3 | 10 | |
| M6 | 6.4 | 12.5 | 0.8 | 
| M8 | 8.4 | 17 | 1 | 
| M10 | 10.5 | 21 | 1.25 | 
| M12 | 13 | 24 | 1.6 | 
| M14 | 15 | 28 | 1.6 | 
| M16 | 17 | 30 | 2 | 
| M18 | 19 | 34 | 2 | 
| M20 | 21 | 37 | 2 | 
| M22 | 23 | 39 | 2 | 
| M24 | 25 | 44 | 2.5 | 
| M27 | 28 | 50 | 2.5 | 
| M30 | 31 | 56 | 2.5 | 
| M33 | 34 | 60 | 3 | 
| M36 | 37 | 66 | 3 | 
| M39 | 40 | 72 | 3 | 
                    
                    


