How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-01 · 6 min read · Independent comparison
• Mijusun Memory Foam Ear — biggest strength: memory foam tips sized specifically for Sennheiser Momentum 3 and 4 TWS, giving a moldable seal that boosts noise isolation and bass.
• Mijusun Memory Foam Ear — biggest trade-off: it's an accessory, not an earbud. If you don't own Momentum 3 or 4, it does nothing for you.
• CaseSack GravaStar Sirius Pro — biggest strength: a semi-hard, water-resistant PEVA shell with an elastic strap and mesh pocket that keeps GravaStar Sirius Pro earbuds and a cable organized.
• CaseSack GravaStar Sirius Pro — biggest trade-off: it's a case only — no device, no cable, no earbuds included — and it's built around one specific earbud model.
• Who each pick is for: Mijusun for Momentum 3/4 owners chasing comfort and a tighter seal; CaseSack for GravaStar Sirius Pro owners who want shock and scratch protection on the move.
This is a three-pair replacement tip kit — sizes L, M and S — made from polyurethane memory foam and shaped 1:1 for the Sennheiser Momentum True Wireless 3 and 4. The whole point of foam over silicone is that it expands to fill the shape of your ear canal instead of pressing against it, and that's exactly the mechanism Mijusun leans on here. The result, per the design, is a firmer, more secure seal that isolates outside sound and, in turn, makes bass and clarity come through more clearly on the earbuds you already own.
The practical upsides show up in everyday situations. If silicone tips slip during workouts, foam's anti-slip grip holds better. If you wear earbuds through a long commute or an all-day work session, the softer material is meant to stay comfortable longer. And because the tips are low-profile and specifically engineered to sit inside the Momentum charging case, you don't lose the convenience of drop-in storage. You also get a small silicone storage box for the spare pairs, plus a one-year warranty.
Who should buy it: anyone who already owns Momentum 3 or 4 earbuds and finds the stock fit loose, uncomfortable, or leaky on noise. Who should skip it: anyone with a different earbud model, and anyone expecting the tips to change the sound signature rather than just improve the seal. It also won't fix a broken earbud — this is a wear-and-tear replacement part, nothing more.
CaseSack's offering is a carrying case, full stop. It's built for the GravaStar Sirius Pro Earbuds 5.2 TWS RGB earphones, and it's a semi-hard zipper shell made from PEVA with a soft, antistatic lining. The job it does is simple and worth taking seriously: it absorbs minor bumps and shakes, resists water, and keeps scratches off earbuds that are, frankly, the kind of product people buy partly because they look good. If you've ever tossed loose earbuds into a bag and pulled them out scuffed, this is the fix.
The interior is where the thoughtful design lives. An elastic strap pins the earbuds down in the base so they don't rattle around, and a mesh pocket in the lid gives you a home for a charging cable or other small accessories. It's compact and light at 1.7 ounces and roughly 3.5 x 2.5 x 2 inches, so it slides into a purse, shoulder bag, or suitcase without eating space — good for home storage and travel alike. It carries a one-year warranty.
Who should buy it: GravaStar Sirius Pro owners who travel, commute, or just want a dedicated storage spot so the earbuds and cable stop living loose at the bottom of a bag. Who should skip it: anyone who doesn't own that specific earbud model, and anyone expecting earbuds or a cable in the box — the package contains the case only, and the device shown is for illustration. The listed fit also references TAGRY X08 as something it can organize, so it's a bit more flexible than a single-model shell, but the primary target is clear.
• Best for improving earbuds you already own → Mijusun Memory Foam Ear. It upgrades fit, comfort and isolation on Momentum 3/4.
• Best for protecting earbuds on the move → CaseSack GravaStar Sirius Pro. Semi-hard PEVA shell, elastic strap, mesh pocket.
• Best for noise isolation → Mijusun. Foam expansion creates the seal; the case does nothing for sound.
• Best for travel organization → CaseSack. Compact, light, water-resistant, with room for a cable.
• Best for all-day comfort and sports → Mijusun. Soft PU foam and anti-slip grip, three sizes to dial in the fit.
• Best for a specific model match → depends on your earbuds. Mijusun is designed 1:1 for Momentum 3/4; CaseSack is designed for GravaStar Sirius Pro.
• Best for a low-commitment purchase → CaseSack. One case, one job, no fit guessing — assuming you own the right earbuds.
• Best for bundling → neither, really. They serve different earbuds, so buying both only makes sense if you own both models.
In my opinion, the honest answer is that these two products shouldn't be competing at all — they're accessories for two different sets of earbuds, and the right pick depends entirely on what's already in your pocket. If you own Sennheiser Momentum 3 or 4 and the fit has never felt right, I'd buy the Mijusun Memory Foam Ear tips; the 1:1 sizing, three-pair kit and foam seal are aimed squarely at the most common complaint about those earbuds. If you own GravaStar Sirius Pro earbuds and need them protected in a bag, I'd buy the CaseSack case instead. Buy the one that matches your earbuds — not the one that sounds better on paper. And check the current price on Amazon before deciding, since both sit in the budget accessory bracket.
what is tws earbuds
TWS stands for "true wireless stereo" — earbuds with no wire between the left and right pieces, each with its own connection. Both products here relate to TWS: the Mijusun tips are made for Sennheiser Momentum TWS earbuds, and the CaseSack case is made for GravaStar Sirius Pro TWS earbuds.
what is tws earbuds means
It means the two earbuds connect to your phone wirelessly and independently, rather than through a cable joining them. That's why accessories like foam tips (for fit and seal) and a hard case (for protection and storage) matter so much — there's no cord to keep them together.
how much is tws earbuds
That varies enormously by brand and model, and neither product here is an earbud anyway — one is a set of replacement tips, the other is a carrying case. For the actual cost, check the current price on Amazon, since the site shows it live rather than quoting a number here.
how to tws earbuds
Pairing is usually the same routine: take both earbuds out of the case, they enter pairing mode, and you select them in your phone's Bluetooth settings. For the fit side of the equation, that's where the Mijusun foam tips come in — swapping to the right size (L, M or S) gives a better seal and, in turn, better sound and isolation.
As an Amazon Associate I earn from qualifying purchases.
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
When you buy through links on this page, we may earn a commission from qualifying purchases at no extra cost to you.
Amazon and the Amazon logo are trademarks of Amazon or its affiliates. This site is an independent third-party review and is not affiliated with, endorsed by, or sponsored by Amazon or the product brands mentioned.
See also: JVC vs Hulaed Invisible Sleep Headphones, Sony WH-CH720N-BLACK vs realme Air 6, Perytong Sleep Headphones vs Fulext Sleep Headphones Headband, Amylove 6 vs Anker Soundcore Space 2: Noise Blocking