Hario MSS-1B: What Changed in the Updated Mini Mill Slim
I remember the frustration of grinding beans with my original Hario MSS-1 and having the grind setting slip halfway through. It happened at least once a week. When Hario released the MSS-1B, their updated Mini Mill Slim with click-stop adjustment, I bought one the same day. That one change fixed my biggest complaint.
The Hario MSS-1B is the second generation of Hario's popular compact manual grinder. It keeps the same ceramic conical burrs and slim body but adds a stepped click adjustment system that locks your grind setting in place. If you've been comparing the MSS-1 and MSS-1B or wondering whether the upgrade is worth it, here's what I've found after using both models side by side.
The Click-Stop Adjustment System
This is the big change, and it genuinely matters. The original MSS-1 used a smooth, stepless adjustment ring held in place by spring pressure. It worked, but it could drift under the force of grinding, especially with harder light-roast beans. You'd start at medium and end up somewhere between medium and fine without realizing it.
The MSS-1B replaced that with a detented click system. Each click moves the burr a fixed, repeatable amount. Turn the ring and you feel a clear, tactile click for each step. To change your setting, you just count clicks from the fully-closed position.
How Many Clicks Do You Get?
I count about 15-18 usable clicks on my MSS-1B. Not all of them produce useful grind sizes. Clicks 1-3 are too fine for anything except Turkish coffee. The practical range breaks down like this:
- Clicks 4-6: Fine, suitable for Moka pot
- Clicks 7-9: Medium-fine, works for AeroPress
- Clicks 10-12: Medium, good for pour over
- Clicks 13-16: Medium-coarse to coarse, French press territory
The steps between clicks are small enough for most people but noticeable if you're trying to make micro-adjustments for espresso dialing. For espresso, you really need a grinder with finer steps between settings. Our best coffee grinder guide covers options with that level of precision.
Grind Quality Comparison: MSS-1 vs MSS-1B
Here's a question I get asked a lot: does the MSS-1B grind better than the original? The honest answer is that the burrs are the same. Hario didn't change the ceramic conical burr set between models. So the particle distribution at any given setting is basically identical.
What did change is consistency between sessions. Because the MSS-1B holds its setting, you get the same grind every time you use it. With the original MSS-1, a slight drift could mean your Tuesday coffee tasted different from your Monday coffee, even with the same beans and technique. The MSS-1B eliminated that variable.
At medium settings, both grinders produce a usable but imperfect grind. You'll see some fines mixed in with the target particle size. My pour overs with the MSS-1B brew in a predictable 3:15 to 3:30 window, which tells me the grind is consistent enough to produce repeatable results.
Build Quality and Design Changes
The MSS-1B looks nearly identical to the MSS-1 at first glance. Same slim profile, same glass grounds container on the bottom, same basic handle design. The differences are subtle but real.
What's the Same
The body is the same plastic and glass construction. The capacity is still about 24 grams. The handle attachment uses the same hex shaft. The overall dimensions are within a millimeter or two. It still fits inside an AeroPress for travel.
What's Different
Beyond the click adjustment, the MSS-1B has a slightly more refined feel to the handle rotation. There's less wobble in the shaft, which I think is a result of tighter manufacturing tolerances rather than a deliberate redesign. The locking nut on top also feels more secure.
The glass jar is the same fragile piece it's always been. Hario hasn't addressed this, and it's still the most likely part to break if you drop the grinder. I wish they'd switched to a polycarbonate jar, but ceramic burr purists would probably revolt.
Grinding Speed and Effort
Grinding speed is identical between the two models. Expect about 1.5 to 2 minutes for 20 grams of medium-roast beans at a medium setting. Light roasts take longer and require more arm effort because the beans are denser and harder.
The short handle on both models limits your torque. After grinding more than 25 grams, my forearm starts to feel it. This is a design limitation of all small-format hand grinders, not specific to Hario. Larger grinders like the Comandante or 1Zpresso JX have longer handles and bigger grip diameters that make grinding physically easier.
If you're grinding for more than one person every morning, the MSS-1B will get tiring. It's designed as a single-serve grinder, and it works best in that role.
Who Should Choose the MSS-1B
If you already own the MSS-1 and the grind drift bothers you, the MSS-1B is a worthwhile upgrade. The click stops alone make the daily grinding routine more predictable and less annoying.
If you're buying your first hand grinder on a budget under $35, go straight to the MSS-1B and skip the original. There's no reason to buy the older version when the updated one costs about the same.
If you want the best possible hand grinding experience and budget isn't the primary concern, the MSS-1B is not where I'd point you. Grinders in the $60-120 range offer steel burrs, faster grinding, and better consistency. Check the top coffee grinder roundup for models that step up significantly in performance.
Cleaning and Maintenance
The MSS-1B follows the same cleaning routine as any manual grinder with ceramic burrs. Disassemble it every week, brush out retained grounds with a small brush, and wash all parts monthly with warm soapy water.
The click-stop adjustment ring collects fine grounds over time, which can make the clicks feel mushy. I blow into the adjustment area after disassembly or use a can of compressed air. This keeps the detents crisp.
Ceramic burrs don't need sharpening and won't rust. They can last for years of daily use. The only risk is chipping from impact (don't drop the burr on tile) or grinding something harder than coffee, like an errant pebble.
FAQ
Is the Hario MSS-1B discontinued?
Hario has released newer models like the Mini Mill Plus and the Ceramic Slim, but the MSS-1B pops up from various retailers periodically. Availability varies. If you find one in stock at a fair price, it's still a good buy.
Can I upgrade my MSS-1 to have click stops?
Unfortunately, no. The click-stop mechanism is built into the adjustment ring and body design. The parts aren't interchangeable between the MSS-1 and MSS-1B. You'd need to buy the MSS-1B as a complete unit.
Does the MSS-1B work for cold brew?
Yes, and it actually does a decent job. Set it to the coarsest position (around click 16-18) and grind your beans. The consistency at coarse settings isn't perfect, but cold brew is very forgiving. The long steep time (12-24 hours) extracts evenly regardless of minor particle variation.
How does the MSS-1B compare to the Timemore C2?
The Timemore C2 costs about $50-60 more but grinds faster, produces more uniform particles, and has a sturdier all-metal body. If you can afford the C2, I'd recommend it over the MSS-1B for daily use. The MSS-1B wins on price alone.
What It Comes Down To
The Hario MSS-1B took the most popular budget hand grinder and fixed its most annoying flaw. Click stops make a real, measurable difference in your daily coffee routine. It's still a budget grinder with budget-grinder limitations, but for under $35, it does honest work.