The Simpson DIA25SS Drop-In Internally Threaded Anchor is a Type 303/304 stainless-steel flush-mount expansion anchor engineered for reliable, permanent fastening in solid concrete. Designed to accept a 1/4-in. threaded rod, this internally threaded drop-in anchor expands mechanically within the base material to create a concealed, flush fastening point - ideal for concrete anchoring applications where a clean, low-profile connection is required. The stainless-steel construction of both the anchor body and expander plug provides enhanced corrosion resistance, making this expansion anchor well suited for demanding environments where standard carbon steel hardware falls short.

Key Features

• Flush-mount expansion design for solid concrete - the anchor sits level with the surface for a clean, concealed finish that works where protruding hardware is not acceptable.
• Internally threaded to accept a 1/4-in. rod - provides a secure, fixed mechanical connection to threaded rod or fasteners, with minimum thread engagement equal to the nominal diameter of the insert.
• Compatible with hand- and power-setting tools - speeds up installation and reduces labor effort, keeping concrete anchoring projects on schedule and within budget.
• Fixed-depth stop bit compatible - drilling to the precise required depth every time reduces guesswork and helps maintain full load capacity by preventing oversized or under-depth holes.
• Requires a 3/8-in. drill bit - a clearly specified drill diameter means crews can prepare the correct tooling in advance and avoid on-site delays.
• Type 303/304 stainless-steel anchor body and expander plug - resists corrosion in moisture-exposed or chemically active environments where plain steel anchors would degrade over time.

Why This Product

• Corrosion-resistant materials throughout - with both the anchor body and expander plug manufactured from AISI 303 stainless steel, this drop-in anchor is built to maintain structural integrity in wet, humid, or corrosive concrete applications where a standard steel anchor would be a liability.
• Flush installation eliminates surface obstructions - the internally threaded, flush-mount design keeps the fastening point fully recessed within the concrete surface, making it the right choice for applications where clearance, aesthetics, or safety requirements rule out exposed hardware.
• Straightforward installation with the right tooling - hand- and power-setting tools combined with a fixed-depth stop bit mean the anchor can be installed quickly, consistently, and correctly without specialized skills, reducing the risk of improperly set anchors that compromise load performance.
• A trusted Simpson anchor in a practical concrete fastening size - engineered to Simpson's specifications with a 1/4-in. rod diameter, 20 TPI UNC threading, and a 1-in. body length, this internally threaded drop-in anchor delivers a well-defined, verifiable performance profile for engineers and contractors specifying concrete fasteners.

Specifications

• MPN: DIA25SS
• Material: Type 303/304 Stainless Steel
• Finish: Type 303/304 Stainless Steel
• Bolt/Rod Diameter: 1/4 in.
• Drill Bit Diameter: 3/8 in.
• Length: 1 in.
• Thread Length: 3/8 in.
• TPI: 20
• Anchor Body Material: AISI 303 - meets chemical requirements of ASTM A582
• Expander Plug Material: AISI 303
• Thread Type: UNC
• Packaging: Packs of 100 and Cartons of 500

Frequently Asked Questions

What base material is the DIA25SS Drop-In Anchor designed for?

The DIA25SS is designed for use in solid base materials, specifically concrete applications where a flush-mount expansion anchor is required.

What size threaded rod does the DIA25SS accept?

This drop-in anchor is designed to accept a 1/4-in. threaded rod. Minimum thread engagement should be equal to the nominal diameter of the threaded insert.

What drill bit size is required to install the DIA25SS?

A 3/8-in. drill bit is required to create the correct-diameter hole for this anchor. A fixed-depth stop bit is also available to ensure you drill to the correct depth every time. Note that oversized holes will make it difficult to set the anchor and will reduce the anchor's load capacity.

Why is Type 303/304 stainless steel used for the DIA25SS?

The anchor body and expander plug are both made from AISI 303 stainless steel, with the anchor body meeting the chemical requirements of ASTM A582. The Type 303/304 stainless-steel construction provides enhanced corrosion resistance compared to standard carbon steel anchors, making it well-suited for environments where moisture or corrosion exposure is a concern.

Note: Product dimensions may differ from picture. Please see item description for specifications.