Dr. Brown's Natural Flow Options+ Replacement Vent Kit is a set of two vents designed for wide-neck bottles. The kit is made of Apto material and is green in color. It is a replacement kit for lost or damaged vents and is compatible with Dr. Brown's Natural Flow bottles. The vents are part of the Options+ system, which allows parents to customize the bottle's venting system to suit their baby's needs. ShipN24H. Inventory location 7639