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The material is SCM435. Alloy steel is heat-processed to increase strength. The height of head is ultra low than the standard ones.
[Size variation]
Unit:mm
| Size（d1） | M3 | M4 | M5 | M6 | |
| Head OD（d2） | 6 | 8 | 9 | 10 | |
| Head height（k） | 1.3 | 1.5 | 1.5 | 1.5 | |
| Socket Width(s) (across flat) | 1.5 | 2 | 3 | 3 | |
| Socket Effect Depth(t)(Max) | 2 | 2.5 | 3 | 4 | |
| Max Torque（N） | 0.8 | 2 | 5 | 5 | |
| Length (L) | 6 | O | O | ||
| 8 | O | O | O | ||
| 10 | O | O | O | O | |
| 12 | O | O | O | ||
| 16 | O | O | O | ||
| 20 | O | O | |||
| 25 | O | ||||
Ultra low head bolt with hex socket