Start with the opening
An insert is sized to the fireplace it goes into and the face is finished with a surround. Measure the height, width and depth of the existing opening before shortlisting a model or a size.
Collection
A gas insert is a sealed gas appliance fitted into an existing fireplace. It replaces an open hearth that loses heat with a closed firebox that burns on demand, with the chimney lined to suit the appliance.
The models here — Napoleon's Rosedale 3 and Oakville, and Majestic's Ruby, Ruby Platinum and Jasper — are direct vent, so they draw combustion air from outside and exhaust through the same lined route and the room air stays separate from the fire. They are listed for natural gas, with propane by special order or conversion, and are ordered together with the vent and liner components and a surround sized to the opening.

An insert is sized to the fireplace it goes into and the face is finished with a surround. Measure the height, width and depth of the existing opening before shortlisting a model or a size.
Direct vent inserts need a lined route to the outside. Vent components and liner kits are configuration-specific, so they are specified together with the appliance rather than chosen afterwards.
These models are listed for natural gas, with propane as a special order or a conversion kit. Ignition, remote, fan and ember media differ by model and are part of the configuration you order.
Brown Chimney can assess what a fireplace would need in your home — the opening, the chimney or venting route, and what work is involved. Service availability depends on your location.
Yes. An insert is fitted into an existing fireplace opening and vented through the existing chimney with a liner. Without a fireplace, a built-in gas fireplace is the product to look at instead.
Compare the published appliance dimensions with the measured height, width and depth of your opening, and check that a surround is offered for the face you need. Brown Chimney can measure the opening and confirm.
The model's own listing. Each insert is ordered in a natural gas or propane configuration and installed with the vent and liner components listed for it, which is why those parts are specified with the appliance.