Hi guys, I just bought a used craft stove model 4380 or 4830, cant remember which. It is an insert with blowers on each end. I noticed it doesnt have firebrick and appears to be a solid molded concrete or other inside. Does this sound normal? Most stoves Ive seen have firebrick. I was just curious if anyone has one like it or knows the type. Ive attached a pic of one like it. Thanks