One of the most common questions pumping parents ask before buying a bag: will my pump actually fit?
It's a fair one. Breast pumps vary significantly in size and design. A full-size double electric like the Spectra S1 has a very different footprint than a wearable like the Willow Go. The wrong bag doesn't just feel cramped: it means your motor rides loose in a main compartment, your tubing tangles, and your milk storage has nowhere to go.
This guide covers every major pump brand and which Sarah Wells bag fits best. Two bags do most of the work: the Allie Sling Bag for wearable and portable pumps, and the Fiona Backpack for full-size double electric pumps. Together they cover the full range of what's on the market in 2026.
Two Bags, Every Pump
Before getting into individual pumps, here's the framework:
Full-size double electric pumps have a dedicated motor unit (typically 8–12 inches), plus tubing, flanges, and bottles. They need a bag with a dedicated insulated side pocket sized for the motor, plus main compartment space for everything else.
Wearable and portable pumps have a much smaller motor footprint, but they come with collection cups, tubing, and accessories that need to be organized and kept accessible. The bag needs structured interior pockets built around smaller components, plus cooler capacity for milk.
The Fiona is built for the first category. The Allie is built for the second.
Wearable and Portable Pumps: The Allie Sling Bag
The Allie Sling Bag ($99) is the lightest bag in the Sarah Wells lineup and the only one designed specifically around how wearable and portable pumps are actually carried. Made from machine washable neoprene with built-in insulation, it works as a cooler bag without adding a separate pouch. The adjustable sling strap wears on either the left or right side.
✔ Secure elastic interior pockets hold wearable pump cups and motors in place while you move
✔ Insulated exterior pocket holds a milk chiller or bottles
✔ Hidden exterior pocket fits a large water bottle or milk container
✔ Exterior zip pocket for your phone and quick-grab items
✔ Top grab handle for hanging on a hook during sessions
✔ Machine washable neoprene with natural insulation
✔ Epic warranty
✔ HSA/FSA eligible
🤱 Willow (3.0, Go, and Go+)
The Willow pumps are designed to sit in-bra during sessions. For transport, you're carrying the motor, collection bags or cups, and accessories. The Willow Go and Go+ motors are compact, and the collection bags fold flat when not in use.
The Allie's elastic interior pockets hold the Willow motor and cups securely. The insulated exterior pocket handles expressed milk during transport.
✔ Best fit: Allie Sling Bag
🤱 Elvie (Stride and Double)
The Elvie pumps have a pod-like shape and sit in-bra during use. Transport involves two cups, a charging case, and accessories, no separate motor unit in the traditional sense.
The Allie's tufted interior pockets handle the cup shape without tipping. The compact footprint is well matched to the Allie's organization.
✔ Best fit: Allie Sling Bag
🤱 Momcozy (M9, S12, and similar wearables)
Momcozy's wearable pumps are cup-style designs with the motor built into each cup. The M9 weighs approximately 10.7 oz and is one of the most popular budget-friendly wearables on the market.
The Allie's interior pockets are designed for exactly this kind of component. Cups sit in the elastic pockets, and the cooler capacity handles milk transport on the way home.
✔ Best fit: Allie Sling Bag
🤱 Eufy Wearable Pumps (S1 Pro and similar)
Eufy's wearable pumps are in-bra cup designs with integrated motors, similar in form factor to Momcozy. The S1 Pro is a premium option with app connectivity and hospital-grade suction.
Same fit principle applies: structured interior pockets for the cups, cooler exterior pocket for milk, compact profile for commuting.
✔ Best fit: Allie Sling Bag
🤱 Baby Buddha
The Baby Buddha is a portable pump with a small motor unit (roughly the size of a deck of cards) that connects to standard collection cups via tubing. It has a dedicated following among exclusive pumpers for its compact size and strong output.
The Baby Buddha motor fits easily in the Allie's interior elastic pocket. Collection cups, tubing, and flanges organize in the remaining space.
✔ Best fit: Allie Sling Bag
🤱 Pumpables Genie Advanced
A portable pump with a small motor unit that connects via tubing, roughly a quarter of the size and weight of the full SuperGenie. Designed for parents who want portability without going fully wearable.
The Allie handles the Genie Advanced the same way it handles the Baby Buddha: motor in the interior elastic pocket, accessories organized around it, cooler pocket for milk.
✔ Best fit: Allie Sling Bag
🤱 Medela Freestyle Hands-Free
The Medela Freestyle Hands-Free is a wearable pump with a motor that can remain in the bag during use, with collection cups connected via tubing. Sarah Wells has a direct collaboration with Medela on the Allie, designed specifically with the Freestyle Hands-Free in mind.
The Allie's interior holds the Freestyle Hands-Free motor while the collection cups are in use. You don't have to remove the pump from the bag during sessions.
✔ Best fit: Allie Sling Bag (designed specifically for this pump)
Full-Size Double Electric Pumps: The Fiona Backpack
The Fiona Backpack ($199) is built for full-size double electric pumps. Machine washable neoprene, double-insulated side pockets, padded laptop pocket, dedicated water bottle or milk chiller pocket, luggage strap, and adjustable backpack straps with a top grab handle.
Fiona pocket dimensions:
-
Smaller side pocket: 9.25"H x 7"W x 5.5"D
-
Larger side pocket: 9.25"H x 7"W x 7.5"D
-
Full bag: 15"H x 13"W x 6"D
✔ Double-insulated side pockets keep milk cold for up to 6 hours
✔ Padded laptop pocket: keeps your tech separate from pump condensation
✔ Dedicated water bottle or milk chiller pocket
✔ Luggage strap for travel
✔ Machine washable neoprene
✔ Epic warranty
✔ HSA/FSA eligible
🔌 Spectra S1 and S2
Among the most popular full-size double electric pumps in the US. Both are hospital-strength closed systems weighing approximately 2.5–3 lbs. The S1 has a built-in rechargeable battery; the S2 plugs in. Functionally the same pump.
The Spectra motor fits cleanly in the Fiona's larger insulated side pocket. The main compartment handles flanges, tubing, and everything else you're carrying to work.
✔ Best fit: Fiona Backpack
🔌 Medela Pump in Style (MaxFlow, Pro, and similar)
Medela's Pump in Style line is one of the most widely used pump families in the US. The motor form factor fits cleanly in the Fiona's larger side pocket. The padded laptop pocket keeps your tech separate from any pump condensation. A real quality-of-life detail if you've ever had a pump drip on your laptop.
✔ Best fit: Fiona Backpack
🔌 Motif Luna
A portable hospital-strength double electric pump weighing under 2 lbs with up to 280 mmHg suction. Compact enough to use with the Allie for a pump-only setup, but if you're commuting with a laptop and a full workday's worth of gear, the Fiona gives you significantly more carrying capacity.
✔ Best fit: Fiona Backpack (or Allie if you want a lighter, pump-only bag)
🔌 Spectra S9
The Spectra S9 is significantly smaller than the S1/S2, roughly 4.5" x 3" x 2.5". Popular as a go-anywhere pump for parents who want double electric performance in a portable package.
The S9 works with either bag depending on how you're using it.
✔ Best fit: Allie Sling Bag (pump-focused, lighter carry) or Fiona Backpack (full workday setup with laptop)
🔌 Cimilre (S6+, S5+, P1, Dual Pro)
Cimilre pumps range from compact portables to full-featured double electrics.
✔ Cimilre S6+ and Dual Pro (compact, portable): Allie Sling Bag
✔ Cimilre S5+ and P1 (larger double electric): Fiona Backpack
Quick Reference: Which Bag for Which Pump
|
Pump |
Best Bag |
|---|---|
|
Willow (3.0, Go, Go+) |
Allie Sling Bag |
|
Elvie (Stride, Double) |
Allie Sling Bag |
|
Momcozy (M9, S12, wearables) |
Allie Sling Bag |
|
Eufy (S1 Pro, wearables) |
Allie Sling Bag |
|
Baby Buddha |
Allie Sling Bag |
|
Pumpables Genie Advanced |
Allie Sling Bag |
|
Medela Freestyle Hands-Free |
Allie Sling Bag |
|
Spectra S1 / S2 |
Fiona Backpack |
|
Medela Pump in Style (MaxFlow, Pro) |
Fiona Backpack |
|
Motif Luna |
Fiona Backpack |
|
Spectra S9 |
Allie or Fiona (depends on use) |
|
Cimilre S6+, Dual Pro |
Allie Sling Bag |
|
Cimilre S5+, P1 |
Fiona Backpack |
Still Deciding? Start Here.
The choice between the Allie and the Fiona usually comes down to one question: are you carrying a laptop?
🔹 Yes, and I want everything in one bag → Fiona Backpack. The main compartment handles your laptop and work gear; the side pocket handles your pump; the whole thing passes as a regular backpack.
🔹 No, I just want the best pump-specific bag → Allie Sling Bag. Built for wearable and portable pump organization in a compact crossbody that doesn't announce itself as a pump bag.
Both are HSA/FSA eligible. Both are machine washable. Both work with every major pump on the market in 2026.
Pump specs referenced from manufacturer product pages. Verify current compatibility with your specific pump model before purchasing.
