Instruct: Classify Amazon reviews into positive or negative sentiment
Query: NOT RECOMMENDED FOR GLASS BOTTLES

I tried to research whether this bottle warmer would work well with my Born Free glass bottles but I was unable to locate information so I ordered it to try it out. Instruction manual states not recommended for glass bottles. I tried to warm my glass bottle anyways but it turned out dangerously hot. I then tried to warm the bottle in the attachment included to warm baby food jars but it did not heat the glass bottle at all. I returned this product and went back to warming my glass bottles by placing them in a mug of hot water.