According to the owners manual the firebricks are 9"x4-1/2"x 1-1/14" but when I tried to fit 2 replacement TSC bricks in they would not fit with 2 bricks side by side. I measured the pumice bricks I removed and found they actually measure 4-3/8" wide VS the claimed 4-1/2" and the TSC bricks were dead on.. I ended up grinding ~1/16" off of the TSC bricks with a masonry wheel in my angle grinder and they fit great now. Now I have the back of the stove lined with 3 of the hard TSC firebricks and saved one of the pumice bricks for side or bottom use where they are not subject to impact 
Ray

Ray