Bought these for my son to use since he loves holding his own bottle but these weren't the best fit for us. They work on the plastic & glass bottles but does take some muscle to get them on but maybe I just didn't have good directions on hold to get them on easily. They don't work well when on the bottle when using a bottle warmer, it seemed to take long for the milk to heat. I suggest warming the bottle then putting the sleeve on. total of 6 sleeves in great condition. Smoke free home. I do not accept returns. Shipping with USPS Ground Advantage.*Food-Safe Soft Silicone for baby self feeding is made of food grade silicone, BPA free, no chemical additives, which is safe to use, especially for teething babies. To avoid contamination, wash after every use.*Easy to hold: Unlike other baby bottle holders, this bottle handles is smoother, softer, and ergonomically designed to provide more gripping power, allowing baby to learn self-feeding faster.*Silicone Bottle Holders: One piece silicone handles with no corners for dirt to accumulate in, baby bottle handle has a good flexibility and twist-resistant capacity. A good condition still remain even if baby pull and twist the handle while learning gripping.*These bottle handles can be used for dishwashers and sterilizers, and high-quality silicone material ensures long-term use.Compatible with Philips Avent natural baby bottles 9oz series, (other series are not applicable) I used them on the 11 oz bottles for a bit they do fit but not all the away to the top like they would on a 9 oz bottles. We switched to a different handle so that my son didn't have to reach so far to be able to use the handles.