Most fireplace glass doors are made of tempered glass with either ceramic or anodized aluminum frames. Glass is placed on the door so that the fire can still be appreciated even with the door closed. Most of these fireplace doors can be bought stock - meaning that most of the door that are for sale can be purchased off the rack and installed with minimal changes.
Not only does it keep me warmer in my home, but oil prices are on the way back up again. The economy is still tight, and every dollar saved adds up during times like these. I can lower the heat in my house and I'll save money on my heating bill as a result. Between the extra warmth and a few dollars saved, I have every reason to recommend looking into fireplace blowers.