M8 x 20mm Socket Button Head Bolts - A2 Stainless Steel - Pack of 4

M8 x 20mm A2 stainless steel socket button head bolts, supplied in a pack of 4. Features a low-profile domed head with a 5mm internal hex (Allen key) drive. ISO 7380 standard. Manufactured from A2 (304) grade stainless steel for excellent corrosion resistance in indoor and outdoor environments.

Fastener Specification

• Standard: ISO 7380
• Thread size: M8 (5/16")
• Thread pitch: 1.25mm
• Length: 20mm (0.79")
• Head type: Button head, low profile domed
• Drive: 5mm hex / Allen key
• Material: A2 stainless steel (AISI 304)
• Finish: Natural stainless
• Pack quantity: 4 bolts
• Weight: approx. 1.76 oz (50g) per pack
• HS Code: 7318 11
• Country of origin: United Kingdom

Key Properties

• A2 (304) stainless steel — excellent corrosion resistance for indoor and outdoor use
• Low-profile button head — clean, finished appearance with reduced snag risk
• ISO 7380 standard — widely compatible with standard hex key sets
• Good clamping force for a button head fastener
• Non-magnetic grade — suitable for food, marine-adjacent, and general engineering use
• Not suitable for high tensile or structural applications

Typical Applications

• Machinery panels and enclosures
• Structural assemblies and fabrication
• Electronics and equipment housings
• Automotive and motorsport applications
• General engineering where a neat low-profile fastener is required

Frequently Asked Questions

What Allen key size fits M8 socket button head bolts?
M8 ISO 7380 button head bolts use a 5mm hex / Allen key drive.

What is the difference between button head and cap head bolts?
Button head bolts have a low-profile domed head that sits closer to the surface, giving a cleaner appearance. Cap head (socket head cap) bolts have a taller cylindrical head that provides higher clamping torque. Button heads are preferred where appearance matters or clearance is limited.

What is A2 stainless steel?
A2 stainless steel (AISI 304) is the most common grade of stainless fastener. It offers good corrosion resistance in most environments and is suitable for outdoor, marine-adjacent, and food-safe applications. For highly corrosive or marine environments, A4 (316) grade is recommended.

What thread pitch is M8?
Standard M8 thread pitch is 1.25mm (coarse thread), compatible with standard M8 nuts and tapped holes.

Are larger packs available?
This listing is for a pack of 4. See our full fasteners range for other pack sizes and thread options.