3-in-1 Flange Sizing Kit, 10 Silicone Inserts 13–21mm
4.6 (2,269)
Our best-loved kit: two inserts in each of five sizes, a silicone ruler and a sponge brush.
7 colours
$9.99
From the nursing nook
Nursi Luna flange sizing kits & pumping essentials
Soft silicone inserts that bring a 24mm shield down to your real size, a pump that works while you hold the baby, and the small things that live beside the chair. Designed with love, providing comfort for mothers.
Most loved3-in-1 flange sizing kits
The quiet hoursPump & parts
- Developed with an IBCLCKits shaped by a lactation consultant
- Food-grade siliconeSoft, BPA-free inserts
- 13 to 21mmFive sizes in one box
- Fits 24mm shieldsMost electric & manual pumps
- Dishwasher safeTop rack, or boil them
- Seven case coloursPick the one for your shelf
The fitting chair
Most of us start pumping in the wrong size.
Pumps ship with a 24mm shield because it is the average, not because it is yours. Measure the nipple across — not the areola — before a session, add about two to four millimetres, and that is the tunnel you want. Try it below with the number on your ruler.
1315171921
Everything in the nook
Four shelves, sixteen things. Every one of them is something we would want within arm’s reach of the chair at 3 a.m.
Flange Sizing Kit, 8 Inserts 15–21mm
5.0 (8)
The same soft inserts without the smallest size: two each of 15, 17, 19 and 21mm.
$14.99
IBCLC-Developed Flange Sizing Kit, 10 or 13 Pack
4.6 (420)
Our newest kit, with a precision ruler and a guide for tracking size changes over the months.
2 packs
from $9.99
Flange Inserts 10 PCS for 24mm Shields, 13–21mm
4.6 (2,267)
The original Nursi Luna insert set that started it all, with ruler and sponge brush.
$9.99
Flange Sizing Kit with 60 Breast Milk Storage Bags
4.3 (17)
Ten inserts and a ruler, plus 60 storage bags for everything the right fit brings out.
$14.99
Breastfeeding Starter Kit: Flange Inserts, Ruler & 50 Nursing Pads
4.1 (17)
Inserts in five sizes, a silicone ruler and 50 individually wrapped disposable nursing pads.
$19.99
15mm Flange Inserts for 24mm Shields, 4 PCS with Case
4.6 (2,267)
Four 15mm silicone inserts, a travel case and a sponge brush.
$8.99
19mm Flange Inserts for 24mm Shields, 4 PCS with Case
4.6 (2,267)
Four 19mm silicone inserts in a carry case — the size many mothers settle on.
$8.99
21mm Flange Inserts for 24mm Shields, 4 PCS with Case
4.6 (2,267)
Four 21mm inserts for the largest step down from a 24mm shield.
$8.99
Wearable Breast Pump, Hands-Free, 2 Modes & 18 Levels
4.1 (19)
A quiet in-bra pump with massage and expression modes and four insert sizes in the box.
$44.99
Replacement Pump Parts Full Set 24mm for Spectra S1, S2 & 9 Plus
4.4 (94)
A complete milk path for a Spectra pump: two 24mm flanges, valves, backflow protectors, tubes and bottles.
$19.99
Valves, Backflow Protectors & Tubing for Spectra S1, S2 & 9 Plus
3.8 (11)
The parts that wear out first, in one bundle: duckbill valves, backflow protectors and tubing.
$15.99
Valves & Diaphragms for Spectra S1, S2 & 9 Plus
The smallest refresh: new duckbill valves and backflow diaphragms.
$7.99
Colostrum Collector Kit, 6 × 5ml Silicone with Storage Case
4.7 (35)
Six soft 5ml collectors, a case and date stickers for the very first drops.
$14.99
Silicone Nipple Ruler for Flange Sizing, with 1.5m Soft Tape
4.6 (312)
A bendable nipple ruler and a soft tape measure for you and the baby.
$5.49
Bottle Washer Detergent Tablets, 150 Count, Fragrance-Free
4.6 (154)
Fragrance-free tablets that clean milk film off bottles and pump parts in any bottle washer.
$18.99
Seven colours, one comfortable fit
The 3-in-1 kit comes in seven case colours. The inserts inside are the same soft, clear silicone — the colour is just for you.
The first weeks homeColostrum, rulers and clean bottlesFor the days when everything is new: collectors for the first drops, a soft ruler, tablets for the washer.
Back at the deskA pump that works while you doOur wearable pump for the laptop hours, and spare Spectra parts for the bag you leave at work.Mothers who found their size
Unedited words from mothers in the United States, from the reviews on our product listings.
★★★★★
SO glad I ordered this!
“I knew I’d been using the wrong size flange but didn’t think it made that much of a difference. Boy was I wrong! I’ve used the appropriate size just once now this morning and it felt so much better and milk flowed WAY faster! I pumped in nearly half the time! It fit perfectly into my Medela flange.”
3-in-1 Flange Sizing Kit, 10 Silicone Inserts 13–21mm
★★★★★
Good Quality and Fit All My Pumps!
“I love this kit!! My flange size has changed a couple times throughout my breastfeeding journey and this kit has all the sizes I have needed. The flanges are great quality and have fit in my spectra, baby buddah 2.0, and momcozy s12. Would highly recommend!”
Flange Inserts 10 PCS for 24mm Shields, 13–21mm
★★★★★
Must have for labor bag
“Hospitals often do not carry the size flange you need. This product allows you to keep measuring yourself as things go and give a wide variety of inserts to get you started pumping. This is esp important if baby is in nicu or for some reason you are unable to breast feed right away. Being able to pump is crucial to success, and you need the right flange size too! I'd love to also see this in even sizes.”
Flange Sizing Kit with 60 Breast Milk Storage Bags
★★★★★
Very nice inserts!
“These are amazing inserts! They are comfortable and easy to insert into a standard 24mm flange. They were easy to use and did not chafe when not lubricated which is a plus because sometimes I would forget my lubricant.”
15mm Flange Inserts for 24mm Shields, 4 PCS with Case
★★★★★
Fantastic
“We have multiple items by Nursi Luna, from baby monitors to these. Great brand. These are fantastic breast pumps that are super quiet and they are actually comfortable to wear. Really simple to use, has some nice settings, the 2 modes are great and all the levels you can choose is perfect. Nice uses. Excellent value. Highly recommend.”
Wearable Breast Pump, Hands-Free, 2 Modes & 18 Levels
★★★★★
Just buy it
“Basically the same as name brand, more bang for you buck and works great. If you feel anxious about this purchase because it's not what comes with your bottle washer, don't. Not had a single problem and even noticed less residue than name brand. Scent free and easy to use.”
Bottle Washer Detergent Tablets, 150 Count, Fragrance-Free
Named for the hours under the moon
Nursi Luna is named for the hours under the moon — the feeds nobody else sees. Everything we make is meant to make those hours a little softer.
Our storyNook notes
Short, practical guides we wish someone had handed us in the hospital.
Sizing · 6 min read
How to Measure Your Flange Size (and Pick the Right Insert)
Pumping should feel like a firm, rhythmic tug — not pinching, not burning. If it hurts, the first thing we check is almost always the size of the…
Wearable pumps · 5 min read
Your First Week with a Wearable Breast Pump
A wearable pump is a small freedom: both hands back, no cord, no sitting still. The first few sessions take a bit of practice. This is what we tell…
Pump care · 4 min read
When to Replace Breast Pump Parts (Valves, Membranes & Tubing)
When a pump feels weaker, most mothers suspect the motor. Nine times out of ten it is a soft valve or a stretched membrane. Here is our replacement…
Asked in the nook
Which pumps do Nursi Luna flange inserts fit?
They are made for 24mm shields and fit most 24mm shields for electric, wearable and manual pumps. Mothers tell us they use them in Medela, Spectra, BabyBuddha and Momcozy shields. They are not designed for 27–28mm shields.
How do I know which insert size to use?
Measure the nipple (not the areola) with the ruler before pumping, then add about 2–4mm. A 16mm nipple usually does well in a 19mm insert. Our flange size guide walks through it step by step, and the size finder on this page does the arithmetic.
Can each side use a different size?
Yes, and many mothers need exactly that. Every insert kit holds two of each size, so the left and right can wear different inserts.
How often should inserts be replaced?
Silicone softens and stretches with daily use. We recommend a fresh pair roughly every one to two months, or sooner if the seal feels weaker.
How do I clean the inserts?
Wash them with warm soapy water and the sponge brush in the kit, run them on the top rack of the dishwasher, or boil them with the rest of your pump parts.
Are the Spectra parts original Spectra parts?
No. They are made by Nursi Luna to fit Spectra S1, S2 and 9 Plus pumps. They are food-grade, BPA-free silicone and the tubing is longer than the original.
Flange sizing kits and breast pump inserts, explained by Nursi Luna
A breast pump flange (also called a breast shield) is the funnel that sits on your breast, and its narrow tunnel is where the nipple is drawn in during pumping. Most pumps are sold with 24mm flanges, yet many mothers measure well below that. When the tunnel is too wide, the areola is pulled in along with the nipple; the result can be rubbing, swelling, slower milk flow and sessions that take far longer than they should. A flange sizing kit solves this without buying a new pump: soft silicone flange inserts sit inside the existing 24mm shield and narrow the tunnel to 21, 19, 17, 15 or 13mm.
Nursi Luna flange sizing kits were developed with an IBCLC (International Board Certified Lactation Consultant) and include a nipple ruler, an instruction guide and a sponge cleaning brush alongside the inserts. To choose a size, measure the diameter of the nipple itself before pumping and add roughly 2–4mm. Many mothers find their two sides measure differently, and sizes change in the first weeks and again months later, which is why our kits hold two inserts in every size.
Our inserts are made from BPA-free, food-grade liquid silicone that is softer than hard plastic, dishwasher safe and easy to boil. They fit most 24mm shields for electric, wearable and manual breast pumps, including the pumps many mothers already own; they are not designed for 27–28mm shields. For mothers who already know their number, single-size packs of 15, 19 and 21mm inserts come with a travel case.
Beyond sizing, the Nursi Luna nook holds a hands-free wearable breast pump with massage and expression modes, replacement valves, backflow protectors, tubing and flanges for Spectra S1, S2 and 9 Plus pumps, silicone colostrum collectors for the first days, and fragrance-free bottle washer tablets. Everything is chosen with one idea in mind: pumping should not hurt, and the right fit is where comfort starts.
Measure your flange size
A step-by-step method using nothing but the ruler in your kit.
Read the guide →Wrong size arrived?
How swaps and returns work through the store where you ordered.
See how swaps work →