Newmac Wb100 firebrick dimensions

[Fauna33]

Hello!!
We recently bought a house with a Newmac Wb100 wood furnace for central heating. But there are no firebricks inside and we’re having a hard time finding the firebrick dimensions on the internet. From the manual it’s 3 bricks against the back wall and 5 on each side, I’m guessing full bricks.
Any help would be appreciated

 

[cygnus]

https://www.manualslib.com/manual/794964/Newmac-Wg-100.html?page=8#manual
Knowing the configuration, you can measure the size of the firebox and determine the size of the bricks. They are usually a standard size.