Strengths: C is the Advent quality, grip is good, good quality plastic, will not slip through your fingers when giving the graduation and do not erase s at 1 glance sponge. Weaknesses: These bottles do not even fall within the high-end bottle of the same brand heater! The teats are too high flow for my daughter of 3 months and even on speed 1 and with a milk thickens, by contrast with the 2 or 1 which tend to become blocked regularly.