Dr. Brown’s™ Narrow Nipple works together with our internal vent system to help babies feed at a pace that’s perfect for them. Each same-level Narrow Nipple provides the same consistent flow rate, so both you and baby know what to expect. These teats are designed specifically for Dr Browns narrow neck plastic and glass baby bottles (not wide neck), others teats won't work with the patented vent system. Pack includes 2x teats for narrow neck bottles.