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Flange Size Guide

Finding Your Perfect Fit

Because comfort and confidence should never be compromised.

At Avari, we believe that every mum deserves a breast pump that works with her body — not against it. That’s why the Avari Neo™ Breast Pump has been thoughtfully designed with comfort, efficiency and customisation in mind.

No two nipples are exactly the same, and getting the right fit matters more than you might think. A well-fitting breast shield can make all the difference when it comes to output, comfort, and long-term pumping success.

Why Fit Matters

An optimal fit means:

  • More efficient milk expression
  • Less discomfort and irritation
  • Better nipple alignment and suction
  • Reduced risk of blocked ducts or damage

Too small, and you may feel pinching or rubbing. Too large, and your areola may be pulled into the tunnel, reducing suction effectiveness.

💡 Did you know? A poor fit is one of the most common reasons mums stop pumping early.

Understanding Breast Shield Sizes

The Avari Neo™ comes in two shield sizes (24mm and 27mm) and 3 additional inserts (17mm, 19mm and 21mm) to suit most mums. But because everyone’s anatomy is unique, we’re working to expand our range of options soon.

To find your ideal size, you’ll want to measure your nipple before a pumping session — when it’s in a relaxed state.


How to Measure Your Nipple Size

To find your perfect fit, you’ll need to measure your nipple diameter—remember, each breast may require a different size.

What you’ll need:

  • A soft measuring tape or ruler
  • A mirror or phone camera for visibility

Step 1: Prepare for Measuring

Gently stimulate your nipple so it stands upright.

Step 2: Measure Your Nipple Size

Using a ruler or measuring Tape, measure your nipple’s diameter (in mm) from base to base. Do not include the areola.

Measure both nipples separately, as sizes may vary.

Step 3: Find Your Perfect Flange Size

Once you’ve measured your nipple, select a flange size that is 1–3mm larger than your nipple measurement:

Find Your Perfect Fit

Nipple Size Recommended Insert Size
13–15mm 15mm Insert
15–17mm 17mm Insert
17–19mm 19mm Insert
19–21mm 21mm Insert
21–24mm 24mm Shield (No Insert)
24mm-27mm 27mm Shield (No Insert)


A well-fitted flange should allow your nipple to move freely within the tunnel without rubbing or excess space. If you’re in between sizes, opt for the larger one — and pay close attention to how it feels.

Signs of a Good Fit

  • Nipple moves freely without rubbing the sides
  • Areola stays mostly outside the tunnel
  • Suction feels gentle, never painful
  • Breasts feel soft and well-drained post-pump

Signs You May Need a Different Size

  • Pain or pinching while pumping
  • Rubbing or blanching (whitening) of the nipple
  • Minimal milk output despite full breasts
  • Redness or swelling after use
TOO LARGE TOO SMALL JUST RIGHT
Aerola pulled in too far, nipples become red and sore. Friction occurs, nipple rubs against flange  causing soreness or discomfort. Nipple moves freely in tunnel, only small amount of the areola is pulled in.

Still Not Sure? We’re Here to Help.

Every mum’s journey is different, and it can take a few tries to find the right fit. If you're unsure, we’re happy to guide you. Reach out to our team for personalised support at support@avari.au.