Designed to use with all Dr. Brown's natural flow baby bottles;These are the same exact pieces that come with each Dr. Brown's natural flow baby bottle meant to replace worn brushes;keeps Dr. Brown's Vent Inserts and Vent Reservoirs clean and clear of blockage.;Top rack, dishwasher-safe;These are the same exact pieces that come with each Dr. Brown's natural flow baby bottle and are meant to replace worn or lost brushes;Helps keep Dr. Brown's Vent Inserts and Vent Reservoirs clean and clear of blockage so the patented internal venting system functions properly