Nursi Luna Flange Sizing Kit Review – IBCLC-Designed Pumping Essentials for Moms

Quick Verdict

I tested the Nursi Luna Flange Sizing Kit for three weeks across different pumping sessions — early morning, midday at work, and late-nightMOTN (mother of the night, if you're not yet fluent in pumping jargon) pumps. The short version: if you've been suffering through sessions with a flange that doesn't quite fit, this kit genuinely helps. The IBCLC-backed sizing logic is sound, the silicone feels gentler on sensitive tissue, and after switching to the correct insert size I noticed a more consistent milk flow and less post-pump tenderness. Rating: 4.3 out of 5 — it earns that score on build quality and thoughtful design, though the 30% output claim needs a grain of salt.

What Is the Nursi Luna Flange Sizing Kit?

The Nursi Luna Flange Sizing Kit is a breast pump accessory set designed to solve one of the most persistent problems in pumping: using the wrong flange size. It includes 10 silicone inserts in five sizes (13, 15, 17, 19, and 21mm), a nipple measurement ruler developed with an IBCLC, and a detailed sizing guide. The inserts are made to nest inside your existing 24mm breast pump shield — essentially reducing the effective tunnel diameter without requiring you to buy all-new flanges.

Unlike generic silicone inserts you might find in bulk on Amazon, this kit comes with professional guidance baked in. The nipple ruler isn't just a paper strip — it's a durable tool designed for repeated use across your entire breastfeeding journey, from those intense early weeks when everything is still settling to later stages when your body changes again. The brand was developed with input from an International Board Certified Lactation Consultant, which means the sizing philosophy is grounded in clinical practice, not just manufacturing convenience.

Key Features

• 10 silicone flange inserts in 5 sizes: 13, 15, 17, 19, and 21mm (2 of each)
• Fits standard 24mm breast pump shields and flanges — not compatible with 27–28mm shields
• IBCLC-developed nipple measurement ruler for accurate sizing
• Food-grade, BPA-free liquid silicone — softer and more flexible than hard plastic
• Designed to improve milk output and reduce discomfort from poor flange fit
• Dishwasher safe; brand recommends replacement every 1–2 months

Hands-On Review

Let me start with the moment I opened the box — because first impressions matter when you're sleep-deprived and managing a newborn. The kit came in clean, minimal packaging with no overwhelming new-plastic smell. The silicone inserts themselves felt noticeably softer than the hard polycarbonate flanges that came with my pump. That difference was immediately apparent in my hand: flex, not rigid.

My first step was the nipple ruler. I've seen print-your-own sizing guides online and frankly they always felt like a rough approximation. The Nursi Luna ruler is sturdier, with clear size markers and a small guide card explaining how to measure mid-pump (when the nipple is most swollen). I measured both sides — 17mm on the left, 15mm on the right. Different sizes, which the packaging explicitly acknowledges as normal. That alone felt like a small revelation. No one had told me before that asymmetry was expected, not a problem.

After switching to the 17mm insert on the left and 15mm on the right, my third session was noticeably calmer. Less tugging, more even suction, and — here's where the data gets personal — I expressed about 10% more volume per session over the next week. I'm being conservative with that number because pumping output fluctuates wildly with hydration, stress, and how many hours of sleep I managed to steal. But the trend was consistent enough that I noticed. The claim of 30% more output feels optimistic to me, but even a 10–15% improvement in comfort and efficiency is meaningful when you're doing this five times a day.

Cleaning was straightforward — I rinsed immediately after each session, then ran everything through the dishwasher on the top rack once daily. No warping, no residue buildup, no weird after-smell. The inserts stayed grippy and flexible through week two, which is when cheap silicone typically starts to go tacky. By week three, I could feel a slight surface change that aligned with the brand's 1–2 month replacement window. That's useful information — now I know when to stock up.

What surprised me was the nipple ruler. I expected to use it once and forget it. Instead, I re-measured at the two-week mark after noticing one side felt slightly different, and sure enough, my left side had shifted up a size. The ruler is now a permanent fixture in my pumping station rather than a one-time tool. That kind of long-term utility is what separates a well-designed product from a clever one.

Who Should Buy It?

• New moms just starting their pumping journey — Getting the right flange size from the start prevents weeks of unnecessary discomfort and inefficient sessions
• Moms experiencing pain, soreness, or low output despite regular pumping — Wrong flange size is one of the most common culprits, and it's often overlooked
• Exclusive pumpers building a stash — If you're pumping 6–8 times daily, every efficiency gain compounds into significant time and volume saved over weeks
• Moms with asymmetry between breasts — This kit gives you two inserts per size, so you can run different sizes without buying two separate products

Skip this kit if: you already own a properly fitting set of inserts in the right sizes and you're not experiencing discomfort. If it ain't hurting, don't fix it. Also, if your pump uses 27–28mm shields natively, these inserts won't fit — check your manual first.

Alternatives Worth Considering

• LactaMed Silicone Flange Inserts — A comparable 6-piece kit at a slightly lower price point; lacks the nipple ruler but includes a good range of sizes. A solid budget alternative if you're confident about your size.
• Kiinde Sizing Kit — Includes multiple insert sizes and integrates with Kiinde's bottle system. Better if you're already bought into that ecosystem, but more expensive and less universally compatible.
• Medela PersonalFit Flex Connectors — If you're deep in the Medela ecosystem and want a manufacturer-backed sizing solution. More expensive per insert, but guaranteed compatibility and brand support.

FAQ

Final Verdict

The Nursi Luna Flange Sizing Kit does exactly what it promises: it takes the guesswork out of flange sizing and delivers a genuinely more comfortable pumping experience. The IBCLC-backed nipple ruler is the standout feature — it's a tool you'll keep using throughout your breastfeeding journey rather than toss after the first week. The silicone quality is solid, the size range covers most moms' needs, and the dual-insert-per-size packaging reflects real anatomical reality.

Is it perfect? No. The 30% milk output claim is aspirational rather than guaranteed, the kit is useless if your pump uses non-24mm shields, and the ongoing replacement cost is something to factor into your budget. But for moms struggling with discomfort, low output, or simple confusion about sizing — this kit is a worthwhile, well-designed solution. I'd recommend it to any pumping mom who hasn't had a proper flange fitting.