Many parents recommend Comotomo or Dr. Brown’s bottles for this age group, as they are well-regarded for reducing nipple confusion and managing colic. For a 2-4 month old, a slow-flow or 'Level 1' nipple is generally appropriate. Keep in mind that every baby is different; some may prefer a specific flow rate for much longer than the packaging suggests, so observe your baby's comfort rather than strictly following age-based milestones on the nipple box.