Hi, we have had to supplement since my son was 5 days old due to a variety of issues. We have found that bottkes work best for us and we like Avent. But recenty, we've been talking about wanting to try glass bottles to avoid leaching toxins into his food. The only ones i have been able to find online are made by Evenflo. Has anybody used these? What do you think of the nipples? Do they cause nipple confusion? Does anyone know of any other brands selling glass bottles?