These bottles are manufactured with a softer BPA-free resin that results in a durable, less brittle bottle with stronger hinges. The softer resin makes opening the bottles easier on your hands but does not affect the odor-reducing seal. We've also made these bottles easier to label. The pinch grip grooves on the bottom of the bottle are compatible with automatic labeling machines and the debossed imprint on the top allows for smooth label application over the top of the bottle. To open, simply squeeze the sides near the top of the vial and hear the "pop" that made these bottles famous.