What's the difference between Superior WRT 4500 and 6000 Series wood burning fireplaces?

The 6000 Series uses Superior's Mosaic Masonry interior liners which are constructed with true kiln-fired firebricks that look just like a masonry fireplace interior. The 4500 Series use a standard poured/cast interior liner more typical with factory built fireplaces. Please give us a call if we can help further. Thanks!