GEIMORI GU38 GRINDER

BENJAMIN SAND - APRIL 2026

Benjamin Sand is the editor of The Mouth and has tested portable projectors, espresso makers, and travel gear across years of nomadic travel through Southeast Asia, Europe, and beyond.

THE VERDICT ⭐⭐⭐⭐ — 4 / 5

Build Quality & Design ⭐⭐⭐⭐⭐ 5/5

Grind Quality — Filter ⭐⭐⭐⭐ 4/5

Grind Quality — Espresso ⭐⭐⭐ 3.5/5

Retention ⭐⭐⭐ 3.5/5

Value for Money ⭐⭐⭐⭐ 4/5

Best For: Home brewers who want an attractive, quiet single-dose grinder primarily for filter coffee, on a budget.

Not For: Serious espresso drinkers, or anyone expecting true zero retention.

Price: ~$159–$199

Possibly the best-looking grinder at this price point on the market. Design aside, the static control is solid, and for filter coffee it does a more than respectable job. The grind uniformity and retention numbers fall short of the "zero retention" marketing claims though, and for espresso the results are inconsistent. But for what it is — a beautiful, capable filter grinder — and you won't be disappointed if you take the plunge and purchase the GU38.

WHAT IS THE GU38?

The Geimori GU38 is a single-dose electric burr grinder from Wirsh, a Chinese coffee equipment brand that has been quietly building a lineup of espresso machines and accessories. The GU38 is the company's counter-top flagship grinder — below it sits the T38 portable battery-powered version, above it the larger GU64 flat burr model.

It features 38mm 6-core conical burrs machined from high-nitrogen SUS420 stainless steel rated at HRC58 hardness, a 96W DC motor running at a steady 190 RPM, 65 stepless grind settings with claimed 0.01mm micro-adjustment precision, a magnetic dosing cup, and an all-metal body with a walnut wood hopper lid.

It ships with bellows, a spray bottle for RDT, and a cleaning brush.

On paper, it reads like a grinder that should cost considerably more than it does. In practice, the picture is a little more nuanced — but still largely impressive for the money.

QUICK SPECS

• Burrs: 38mm 6-core conical burrs (SUS420 Stainless Steel, HRC58 hardness).
• Motor: 96W DC motor at a steady 190 RPM.
• Adjustment: 65 stepless grind settings (0.01mm precision).
• Build: All-metal body with a walnut wood hopper lid.
• Included: Bellows, RDT spray bottle, magnetic dosing cup.
  

WHO IS WIRSH/GEIMORI?

Wirsh is an American-registered company with Chinese manufacturing roots, founded with a focus to excel in home espresso and coffee equipment. The Geimori grinder line — launched originally as a Kickstarter with their flat burr GU64 and GU78 models — generated genuine specialty coffee industry attention when Sprudge covered it in 2024, describing the feature list as reading "like a deeply nerdy Reddit r/coffee thread."

The GU38 is their most accessible entry point, with conical burrs, smaller footprint, lower price — but built with the same all-metal philosophy and aesthetic as the rest of the range. This is not a brand pumping out white-label generic gear. There is genuine engineering intent here, even if the execution is not flawless at this price point.

DESIGN - WHERE IT GENUINELY EXCELS

The GU38 is, without question, one of the most attractive coffee grinders available at this price. The all-metal body in matte black (or white), the walnut wood hopper lid, the compact footprint — it looks like it costs three times what it does. At 5.5 pounds and 3.5 x 6 x 12 inches, it is light and slim enough for small kitchens and genuinely beautiful enough to sit proudly on any counter.

The magnetic dosing cup is a genuinely smart design touch — it clicks into place under the chute cleanly every time, reducing mess and making the workflow feel polished. The 65-click stepless dial is smooth and feels premium to turn, and the single-button operation keeps things simple. The included spray bottle for RDT and the bellows for clearing the chute are both actually useful rather than box-filling accessories.

This thing does not feel cheap in the hand. At all.

GRIND SIZE & RETENTION

Here is where we need to slow down and look at the actual data rather than the marketing copy — because there is a gap between what is claimed and what independent testing shows, and you deserve to know about it before spending your money.

Retention — The Real Story

Wirsh markets the GU38 as having "zero retention" with less than 0.1g retained per dose when using RDT. Independent testing by Tom's Guide, using a Fellow Tally Pro scale across three consecutive 20g doses, found an average retention of 1.67% — meaning approximately 0.33g of coffee stayed in the grinder per dose. For context, the Varia VS3 measures 0.75% retention, the Baratza Encore ESP 1.55%, and the Breville Dose Control Pro a worse 2.15%.

So the honest picture: the GU38 is not zero retention, but it is not bad retention either. It sits in the middle of the pack. With RDT and the bellows, you will get that number lower — closer to the 0.1g claimed — but under normal use conditions it is around 0.33g per dose.

For a single-dose grinder, this is something to be aware of, especially if you are rotating between expensive specialty coffees where cross-contamination matters.

Grind Uniformity — Filter vs Espresso

At medium grind settings for filter coffee — around the 30-40 range (in our tests) — the GU38 performs well enough to produce enjoyable, balanced pour-overs. The 38mm conical burrs do a reasonable job and the result in the cup for V60 and Chemex brewing is genuinely pleasant.

At espresso settings the picture becomes more complicated. Lab sieve testing of fine grind (setting 5) showed that only 50% of grounds passed through the 300-micron sieve, meaning fully half the grounds were smaller than Turkish grind — while 20% were simultaneously in the 500-800 micron range typical of Chemex. In practical terms this means you have a bimodal distribution: very fine particles and relatively coarse particles mixed together, which produces inconsistent extraction, channeling risk, and unpredictable shot quality.

For a grinder marketed as capable of "professional espresso" and "perfect 9-bar extraction," this is a tad exaggerated. It will pull espresso, and many home users report enjoyable shots, but if you are pulling on a high-end machine with precision baskets and expecting competition-level consistency, the GU38 will not deliver that.

Grind Speed

At 190 RPM the motor is quiet — measured at 75dB, noticeably quieter than the Baratza Encore ESP and comparable to the Eureka Mignon Specialita, though louder than the Varia VS3's whisper-quiet 67dB.

The trade-off is speed: 20g at a medium grind setting takes around 39 seconds. This is not a dealbreaker — it is the same as the VS3 and a natural characteristic of low-RPM DC motors, but worth knowing if you are making multiple doses in quick succession.

Dark Roasts

Since we do not use dark-roast beans, we did a bit of hunting and some users online have flagged that oily dark roast beans can clog the conical burrs, requiring more frequent cleaning. If you drink predominantly dark roasts, this is a grinder to approach with caution. We tested the machine with Medium and Light roast coffee, so we cannot comment 100% on this.

For medium and light roast specialty coffee it performs considerably better.

The Positives

The Build — Metal construction with walnut wood accents. It looks amazing for the price and feels solid in the hand.

The Quiet Motor — 75dB is genuinely impressive for an electric grinder at this price.

The Workflow — Everything you need is in the box and it all works cleanly.

The Static Control — For all the retention caveats, the static levels are genuinely low. Just use a spray bottle.

The Filter Performance — For V60, Chemex, Aeropress, the GU38 produces pleasant, balanced cups. It does not accentuate acidity and florals, but it creates a sweet and balanced cup that works well with any bean origin.

The Stepless Dial — 65 settings with claimed 0.01mm micro-adjustment is excellent for a grinder at this price. The ability to make tiny incremental adjustments between brew sessions is something you normally pay more for.

The Negatives

The Retention Gap vs Claims — "Zero retention" is aspirational marketing. Real-world average retention of 1.67% with bellows is fine but not zero.

Espresso Uniformity — Bimodal grind distribution at fine settings means inconsistent espresso extraction. This is not a precision espresso grinder despite the marketing language.

Dark Roast Compatibility — Oily beans and the 38mm conicals do not always agree. Lighter and medium roast specialty coffee is this grinder's comfort zone.

Grinding Speed — 39 seconds for a 20g dose is on the slow side for a counter-top electric grinder. Not a dealbreaker but worth knowing.

Auto Switch-off — I feel this would have been a nice feature, as grinders that you manually have to turn OFF are a bit distracting for workflow. However, at the price I can understand why this wasn't a priority.

Finishing — As seen in the photo above, the etching of the numbers on the dial are done poorly. This is an area that escaped the team in charge of checking finishing standards.

Charging Brick - The power cable is huge, something that they could have made a lot smaller in footpring, to really look sleek on a counter-top. Their machine looks super minimal, so the power box could have been designed with a bit more intentionality.

Final Thoughts

The GU38 is a grinder that will genuinely impress you in some areas and quietly frustrate you in others — and the key is knowing which category you fall into before buying.

If you drink mostly filter coffee, want something beautiful on your counter, appreciate a quiet motor and a clean workflow, and are working with a budget around $160-200, this is an excellent choice.

It over-delivers on design, handles filter coffee well, and ships with a complete accessory kit that rivals what much more expensive machines include.

If you pull serious espresso daily, rotate through oily dark roasts, or need true single-dose zero-retention performance, you are going to run into the limitations fairly quickly — and at $199 the Baratza Encore ESP is a more consistent espresso grinder, even if it cannot touch the GU38 on aesthetics.

Buy this for what it is — a beautiful, honest filter grinder with solid filter cup quality and a great workflow — rather than what the marketing says it is, and you will be very happy with it.

BUY THIS IF:

• You drink primarily filter coffee — V60, Chemex, Aeropress
• Counter aesthetics matter to you, it is truly stylish
• You want a quiet early morning grinder
• You are on a budget around $160-200 and want the best looking option in that range
  
  

SKIP THIS IF:

• You pull precision espresso daily and need true grind uniformity
• You drink predominantly dark, oily roasts
• You need proven zero-retention performance
• You have the budget to step up to the Varia VS3
  
  

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