The short answer: match the bottle to the feed, not the calendar
Lansinoh offers two bottle sizes in this lineup: 5oz and 8oz. Both use the same NaturalWave nipple and are designed for breastfed babies, so the real decision is capacity. The 5oz bottle is a practical starting point for smaller feeds and early breast milk storage, while the 8oz bottle gives you room as feeding volumes grow. Neither size comes with a stated age range in the supplied information, so let your baby's feeding patterns guide you rather than a fixed schedule.
5oz vs 8oz at a glance
The two bottles share the same nipple technology and safety materials. The main differences are capacity and the pack sizes available.
- Capacity: 5oz (product 3425751) vs 8oz (product 3425752). Choose based on how much you typically feed or store per session.
- Pack options: The 5oz bottle is available as a Single, 3-Pack, or 4-Pack. The 8oz bottle comes as a 3-Pack or 4-Pack.
- Nipple: Both include the NaturalWave Nipple, which is 100% silicone and clinically proven to reduce nipple confusion.
- Venting: Both feature the Air Ventilation System (AVS), which reduces intake of gas, a potential cause of colic or spit up.
- Material: Both bottles are made from polypropylene plastic and are BPA and BPS free.
When the 5oz bottle makes sense
The 5oz bottle is a good fit for early breastfeeding journeys and for storing smaller pumped amounts. Because it is shorter, it can be easier to handle during those first weeks. If you are building a stash or pumping occasionally, the 5oz size lets you store modest volumes without leaving a lot of empty space. The single-bottle option is also useful for trying the NaturalWave nipple before committing to a multi-pack.
When to move up to 8oz
As your baby's feeds grow, the 8oz bottle gives you more capacity per feed and per storage container. If you find yourself frequently filling the 5oz bottle to the top or needing to prepare a second bottle, the 8oz size can streamline your routine. The 8oz bottle is also handy for storing larger pumped volumes in the fridge or freezer. Keep in mind that the supplied information does not specify a maximum fill line beyond the stated capacity, so follow the bottle's markings and your baby's cues.
Key features shared by both sizes
- Baby Bottles 5oz: NaturalWave Nipple is 100% silicone, soft, flexible, and designed for optimal compression. The nipple is the same across both sizes, so you are not trading off nipple preference when you choose capacity.
Baby Bottles 5oz - Baby Bottles 8oz: Air Ventilation System (AVS) reduces intake of gas, a potential cause of colic or spit up. Venting is consistent across sizes, so the decision remains about how much milk you need to hold.
Baby Bottles 8oz - Baby Bottles 8oz: BPA and BPS free. Both bottles meet the same material safety standard, so you can choose based on capacity alone.
How bottle size fits into pumping, storing, and feeding
Lansinoh bottles are part of a Pump-Store-Feed approach: you can pump directly into the bottle, attach the collar with the NaturalWave Nipple to feed right away, or seal the bottle with a cap to store breastmilk. The wide neck is designed for a seamless transition between these steps. The 5oz size works well for smaller pump sessions or for storing smaller portions, while the 8oz size suits larger volumes. The supplied information does not specify whether both sizes are compatible with all breast pumps, so check your pump's instructions if you plan to pump directly into the bottle.
Nipple flow: one size does not fit all
Both bottles come with a NaturalWave Nipple, but flow rate is a separate choice. Lansinoh offers slow, medium, and fast flow nipples to match your baby's needs. You can identify the flow by the marking on the bottom rim: slow-flow reads “Size 2S,” medium-flow reads “Size 3M,” and fast-flow reads “Size 4L.” The supplied information does not state which flow comes with the 5oz or 8oz bottle by default, so check the packaging or product listing. If your baby seems frustrated or feeds too quickly, you may need to try a different flow.
Cleaning and warming: what to know before you buy
Both sizes are dishwasher safe on the top rack only, though hand washing the NaturalWave Nipple is recommended to extend its life. You can sanitize bottles and nipples by boiling them in water, but make sure there is ample water in the pot and that no parts touch the bottom or sides, as this could cause them to melt. Do not heat breastmilk or the bottle in a microwave, as microwaving can create hot spots and damage breastmilk nutrients. Instead, warm milk in the bottle or a storage bag using a container of warm water. Lansinoh does not currently make a bottle warmer.
Making the choice
If you are primarily feeding a newborn or storing smaller pumped amounts, start with the 5oz bottle. If your baby is taking larger feeds or you want to store bigger volumes, the 8oz bottle is the practical upgrade. Many parents end up using both sizes: 5oz for early days and 8oz as feeding volumes increase. Because both share the same nipple and venting system, you can switch sizes without changing the feeding experience.
