M6 M8 Extra Long Masonry Expansion Bolts — Concrete Wall Anchor Screws (30–80mm)

A general rule: the bolt length should be at least 1.5× the thickness of the material being fastened, plus the embedment depth into the base material. For example, fastening a 10mm bracket into concrete typically requires at least a 30mm (≈1-3/16") bolt. For heavier loads or thicker fixtures, choose 60mm (≈2-3/8") or 80mm (≈3-1/8") options. When in doubt, go longer — you can always trim embedment depth with a washer, but you can't extend a bolt that's too short.

Load capacity depends on bolt diameter, embedment depth, and base material strength. Generally, M6 expansion bolts in solid concrete can handle tensile loads of approximately 1–2 kN, while M8 bolts typically support 2–4 kN under similar conditions. Shear capacity is typically higher. Always consult a structural engineer for safety-critical or overhead applications — these figures are general estimates and vary with installation quality and concrete grade.

The stainless steel variants are generally suitable for outdoor and damp environments, offering corrosion resistance in most weather conditions including rain exposure and moderate humidity. The black oxide (black finish) variants are better suited for dry indoor use — the black oxide coating provides only mild corrosion protection and will rust over time if exposed to moisture.

These expansion bolts use standard metric coarse threads — M6 (1.0mm pitch) and M8 (1.25mm pitch). They are compatible with standard metric nuts, washers, and fixtures. They are not compatible with UNC or UNF inch-standard hardware. If your existing fixtures use SAE/imperial threads, you will need an adapter or different fastener.

These expansion bolts are designed for solid base materials including poured concrete, concrete block (solid), brick, and natural stone. They are generally not recommended for hollow block, lightweight aerated concrete (AAC), drywall, or soft materials where the expansion sleeve cannot grip the bore wall properly. For hollow substrates, consider toggle bolts or hollow-wall anchors instead.

Choose stainless steel for outdoor installations, high-humidity areas, coastal environments, or anywhere long-term corrosion resistance is a priority. Choose the black oxide finish for indoor projects where aesthetics or budget are the main consideration — the dark finish blends well with dark surfaces and is typically more economical per piece. Both finishes use the same wedge-expansion mechanism and are available in M6 and M8 sizes.

Each size option contains 20 pieces per bag. At checkout you can select 1 bag (20 pcs), 3 bags (60 pcs), or 5 bags (100 pcs) — bulk packs offer a lower per-piece cost for larger jobs. The expansion bolt sets are a separate configuration that includes 4 complete anchor assemblies (bolt + sleeve + nut + washer) per pack, available in stainless steel or iron.