Dimensions (Nominal diameter d × Length L)	Common length range (mm)	grade	description
M6	20, 25, 30, 35, 40, 50, 60, 80, 100	4.8 8.8	Basic general-purpose specifications, suitable for light structures and everyday equipment fixing.
M8	25, 30, 40, 50, 60, 80, 100, 120, 150	8.8	One of the most frequently used specifications, balancing strength and versatility.
M10	30, 40, 50, 60, 80, 100, 120, 150, 200	8.8 10.9	Mainstream medium-sized specification, with stronger load-bearing capacity and extremely wide application.
M12	40, 50, 60, 80, 100, 120, 150, 200, 250, 300	8.8 10.9	Preferred for heavy-duty applications, for connections requiring the ability to withstand large loads or vibrations.
M16	Customization available upon request.	8.8 10.9	Large heavy-duty structural components, such as large steel structure workshops, bridges, and heavy equipment bases.

Performance grades: Grade 4.8  hdg hex bolt is for commonly used standard parts, Grade 8.8 hdg hex bolt is the mainstream choice for high strength, and Grade 10.9 hdg hex bolt is used for critical parts that withstand severe impacts and vibrations.