How to measure (60 seconds)
- Opening width & height: measure your framed rough opening (built-in) or existing fireplace opening (insert).
- Depth available: confirm you have the required depth for your model (10" for 26–42; 12" for 54").
- Power plan: decide built-in hardwire vs insert plug-in (cord) and plan a dedicated circuit.
- Finish needs: for inserts, plan surround kit coverage if your existing opening is oversized.
Clearance note
Keep furniture, drapes, bedding materials and all combustible materials at least 3 feet from the front of the fireplace. Follow the manufacturer’s clearance instructions and local code for mantels, shelves, and TV installations.
Fit requirements table (hard constraints)
Finished opening dimensions below are the minimum per the manual (built-in framing and minimum insert opening). Use the installation selector below to choose built-in vs insert notes.
| Size | Model (SKU) | Viewing area (W×H) | Firebox (W×H×D) | Recessed framing / cutout (W×H×D) | Heat (standard) | Heat (optional) | Power + breaker | Link |
|---|---|---|---|---|---|---|---|---|
| 26" | RS-2621 | 22 3/4" W × 15 3/8" H | 26" W × 20 7/8" H × 9 7/8" D | 23" W × 18 3/4" H × 10" D | 120V 60Hz, 1465W, 5,000 BTU | — | Dedicated 120V circuit recommended. Use a dedicated 15 Amp (or higher) breaker (per manual). |
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| 30" | RS-3021 | 28" W × 15 3/8" H | 31 1/4" W × 20 7/8" H × 9 7/8" D | 28 1/4" W × 18 3/4" H × 10" D | 120V 60Hz, 1465W, 5,000 BTU | — | Dedicated 120V circuit recommended. Use a dedicated 15 Amp (or higher) breaker (per manual). |
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| 36" | RS-3626 | 32 3/8" W × 20 1/2" H | 35 3/4" W × 26" H × 9 7/8" D | 32 5/8" W × 23 7/8" H × 10" D | 120V 60Hz, 1465W, 5,000 BTU | — | Dedicated 120V circuit recommended. Use a dedicated 15 Amp (or higher) breaker (per manual). |
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| 42" | RS-4229 | 38 1/2" W × 23 1/2" H | 41 3/4" W × 29" H × 9 7/8" D | 38 3/4" W × 26 3/4" H × 10" D | 120V 60Hz, 1465W, 5,000 BTU | — | Dedicated 120V circuit recommended. Use a dedicated 15 Amp (or higher) breaker (per manual). |
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| 54" | RS-5435 | 50 11/16" W × 29 1/2" H | 54" W × 35" H × 12" D | 50 15/16" W × 32 3/4" H × 12" D | 120V 60Hz, 1465W, 5,000 BTU | — | Dedicated 120V circuit recommended. Use a dedicated 15 Amp (or higher) breaker (per manual). |
View on product page |
Installation type selector
Pick your install method to see the right constraints and wiring notes.
Built-in mounted: finished opening minimums
Use the “Recessed framing / cutout” dimensions in the table. Depth is 10" for 26–42 models and 12" for the 54" model (per manual).
Wiring: Built-in installations are designed to be hardwired. Keep the fireplace on a dedicated 120V circuit and use a dedicated 15 Amp (or higher) breaker (per manual). Use a qualified electrician and follow local code.
Clean-face finishing
All Redstone models include a trim kit to support clean-face built-in finishing where tile/stone can return neatly to the opening.
Insert mounted: existing fireplace opening
Your existing opening must meet or exceed the minimum “Recessed framing / cutout” dimensions in the table. Insert installations plug into a grounded receptacle (power cord supplied) and should be on a dedicated circuit.
Surround kits: 26", 30", and 36" models support optional insert surround kits (including wider options) to cover gaps between the fireplace and your existing masonry opening. 42" and 54" are typically finished as clean-face built-ins (no surround-kit coverage required).
Size-by-size guidance (recommendations)
The Redstone series uses Hybrid-FX™ flame technology and independent lighting control for flames, ember bed, and downlighting. The fit table above is the source of truth for opening sizes.
26" model
RS-2621
Best for: Small apartment fireplaces, bedroom inserts, or tiny home built-ins.
Why: This is the most compact unit in the series, designed to fit into smaller "Zero Clearance" wood-burning fireplaces. It allows you to add the ambiance of a real fire to intimate spaces where a larger unit simply won't fit, all while running on a standard 120V plug.
Viewing area: 22 3/4" W × 15 3/8" H
Recessed cutout: 23" W × 18 3/4" H × 10" D
Firebox: 26" W × 20 7/8" H × 9 7/8" D
30" model
RS-3021
Best for: Standard-sized masonry fireplace inserts and cozy living room built-ins.
Why: The 30-inch model is the industry standard for fireplace retrofits. It balances a generous viewing area with a chassis size that fits the majority of mid-sized existing fireplace openings. It’s the go-to choice for homeowners looking to replace a messy log grate with a clean, efficient Hybrid-FX™ flame.
Viewing area: 28" W × 15 3/8" H
Recessed cutout: 28 1/4" W × 18 3/4" H × 10" D
Firebox: 31 1/4" W × 20 7/8" H × 9 7/8" D
36" model
RS-3626
Best for: Large traditional family room fireplaces and "Feature Wall" built-ins.
Why: At 36 inches, the viewing area becomes significantly more vertical and commanding. It mimics the scale of a large open-hearth fireplace. This is the largest size that supports the optional Insert Surround Kits, making it the premium choice for high-end fireplace renovations.
Viewing area: 32 3/8" W × 20 1/2" H
Recessed cutout: 32 5/8" W × 23 7/8" H × 10" D
Firebox: 35 3/4" W × 26" H × 9 7/8" D
42" model
RS-4229
Best for: New construction "Built-in" projects and grand master suites.
Why: The 42-inch model is designed primarily as a built-in focal point. Because it does not use a surround kit, it offers a "Clean-Face" finish where the stone or tile comes right to the edge of the glass. It provides a massive, high-intensity flame display that anchors a large room beautifully.
Viewing area: 38 1/2" W × 23 1/2" H
Recessed cutout: 38 3/4" W × 26 3/4" H × 10" D
Firebox: 41 3/4" W × 29" H × 9 7/8" D
54" model
RS-5435
Best for: Great rooms, luxury estates, and commercial lobbies.
Why: This is the "Statement" piece of the Redstone line. With a nearly 3-foot tall viewing area, it offers a massive vertical flame presence that creates a true "lodge" feel. It requires a 12-inch deep wall cavity, rewarding the deeper installation with an incredible sense of firebox depth and realism.
Viewing area: 50 11/16" W × 29 1/2" H
Recessed cutout: 50 15/16" W × 32 3/4" H × 12" D
Firebox: 54" W × 35" H × 12" D
View product page and availability
Check current stock, select a size, and see current pricing on the main product page.
Safety and electrical notes are summarized from the Modern Flames Redstone owner’s manual and Redstone trim/spec flyers. Always follow the manufacturer installation instructions and local electrical code. Use a qualified electrician for hardwire installation.