Orbit FA-4SB-MKO-EXT Welded Fire Alarm Extension Ring, 4" Square Steel

Orbit FA-4SB-MKO-EXT Welded Fire Alarm Extension Ring, 4" Square, 1-1/2" Deep

The Orbit FA-4SB-MKO-EXT is a 1-1/2" deep, 4" square fire alarm extension ring built from 16 gauge sheet steel and finished with a fully welded seam construction for long-term structural integrity. Designed to add usable depth to standard 4" square electrical and fire alarm boxes, this extension ring provides 21-cubic-inch of additional interior volume, giving installers the room needed for wire fill, device mounting, and conduit routing in fire alarm circuit installations. The ring is equipped with MKO (multiple knockout) openings on the sides, allowing conduit entry from multiple directions without the need for field drilling. Its welded-seam design eliminates the loose joints and gaps found in crimped or tabbed extension rings, delivering a rigid, code-ready enclosure extension for commercial and industrial fire alarm wiring applications. Orbit Industries manufactures this extension ring to integrate directly with standard 4" square boxes, making it a straightforward retrofit or new-construction accessory for electricians and fire alarm technicians who need extra box depth without replacing the entire enclosure.

Key Features

• Trade Size: 4" x 4" x 1-1/2" deep extension ring, adding 21-cubic-inch of usable box volume for wire and device fill.
• Durable Construction: Fabricated from 16 gauge sheet steel for a rigid, impact-resistant extension that holds up under jobsite handling.
• Welded Seam Design: Fully welded construction (Straight Blade-MKO-EXT) eliminates loose seams for a solid, one-piece extension ring.
• MKO Knockouts: Multiple knockout openings provide flexible conduit entry points from several directions without field modification.
• 4" Square Compatibility: Sized to mate directly with standard 4" square boxes commonly used in fire alarm and low-voltage circuits.
• Added Interior Volume: The 1-1/2" depth and 21-cubic-inch capacity give installers extra room for splices, devices, and conduit fill.

Technical Specifications

• Material: 16 Gauge Sheet Steel
• Dimensions: 4-Inch x 4-Inch x 1-1/2-Inch
• Interior Volume: 21-Cubic-Inch
• Seam Type: Fully Welded
• Knockout Configuration: MKO (Multiple Knockout)

Typical Applications

• Fire Alarm Circuit Box Extensions
• Commercial and Industrial Low-Voltage Wiring
• 4" Square Box Depth Retrofits
• Conduit Fill and Splice Volume Expansion
• New Construction and Renovation Fire Alarm Installations

Why Orbit?

Orbit Industries builds this extension ring from 16 gauge sheet steel with a fully welded seam, giving electrical and fire alarm contractors a rigid, dependable accessory for expanding 4" square box depth. The MKO knockout configuration adds installation flexibility, while the welded construction ensures the ring holds its shape and alignment through demanding jobsite conditions, making it a reliable choice for professional fire alarm and low-voltage wiring work.