304 Stainless Steel Hollow Socket Cap Screws M3–M12 Allen Bolt

304 Stainless Steel Hollow Socket Head Cap Screws – M3 to M12

Engineered for precision applications, these 304 stainless steel hollow socket head cap screws feature a through-hole (venting) design that makes them ideal for applications requiring fluid passage, gas venting, wire routing, or pressure equalization. With a standard hex socket (Allen) drive, they install quickly and securely using any standard Allen key or hex bit.

Available Sizes & Through-Hole Dimensions

• M3 — Through-hole: 1.5 mm
• M4 — Through-hole: 2.0 mm
• M5 — Through-hole: 2.5 mm
• M6 — Through-hole: 3.2 mm
• M8 — Through-hole: 4.2 mm
• M10 — Through-hole: 5.2 mm
• M12 — Through-hole: 6.2 mm

Key Features

• Grade 304 Stainless Steel — Excellent corrosion resistance for indoor and outdoor use
• Hollow / Venting Through-Hole — Allows fluid flow, air venting, or wire pass-through along the bolt axis
• Hex Socket (Allen) Drive — Easy installation and removal with standard Allen keys or hex drivers
• CE Certified — Meets applicable European conformity standards
• Customizable — Available in a range of metric thread sizes from M3 to M12
• No High-Concern Chemicals — Safe for a wide range of applications

Typical Applications

• Pneumatic and hydraulic systems requiring vented fasteners
• Electronics enclosures needing wire pass-through bolts
• Precision machinery and instrumentation assemblies
• DIY electrical and fabrication projects
• Automotive, industrial, and marine environments

Made in Mainland China.

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Frequently Asked Questions

Q: What is a hollow socket head cap screw and what is it used for?

A: A hollow socket head cap screw (also called a through-hole or venting bolt) has a continuous axial hole drilled through its entire length. This allows air, gas, fluid, or thin wires to pass through the bolt. They are commonly used in pneumatic systems, hydraulic assemblies, electronics enclosures, and precision instruments where standard solid bolts would block the required passage.

Q: What material are these hollow Allen bolts made from?

A: These bolts are manufactured from Grade 304 stainless steel, which offers excellent resistance to rust, oxidation, and corrosion, making them suitable for both indoor and outdoor environments as well as mild chemical exposure.

Q: Which Allen key size do I need to install these bolts?

A: Each metric size uses a standard hex socket drive. The required Allen key (hex key) size corresponds to the standard DIN 912 specification for each thread size — for example, M3 uses a 2.5 mm hex key, M4 uses a 3 mm hex key, M5 uses a 4 mm hex key, M6 uses a 5 mm hex key, M8 uses a 6 mm hex key, M10 uses an 8 mm hex key, and M12 uses a 10 mm hex key.

Q: Are custom lengths or quantities available?

A: Yes, these hollow socket head cap screws are listed as customizable. Please contact us directly if you require a specific length, quantity, or other specification not shown in the standard listing.

Production & Packaging Notice

To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.