3 or 4 sided gas fire?

[Backboiler]

Apart from the obvious, does anyone know the difference between a 3 and a 4 sided fire as per the following link? The manufacturer states that the 3 sided will fit into a standard opening but I'd like to know more. Like where is the missing side? Crystal Fires - Royale

 

[lame plumber]

can only think 3 sided = open front and 4 sided = glass fronted. simplesss

 

[Backboiler]

can only think 3 sided = open front and 4 sided = glass fronted. simplesss

Thanks and good response but I quote the manufacturer "A perfect compliment to any contemporary fireplace, the Royale 3 sided fits into a standard 16” fireplace opening and is available with both the Gem open fronted and the Montana H.E glass fronted fires.
This suggests that a 3 sided may have a glass front

 

[Orry Clayton]

not 100% sure but i think the 3 side is like a standard ILFE. The 4 sided would be what they call a cassette fire, this is one that isn't sat on the hearth, but built up in to the chimney.

 

[tom609]

4 sided probably hole in the wall appliance

 

[buckley plumb]

not 100% sure but i think the 3 side is like a standard ILFE. The 4 sided would be what they call a cassette fire, this is one that isn't sat on the hearth, but built up in to the chimney.

agree link even shows that a harth mounted fire and a casset hole in the wall fire

 

[Backboiler]

agree link even shows that a harth mounted fire and a casset hole in the wall fire

Sorted. Thanks for the help folks!