Boba U4 vs U4T (vs Holy Boba)

Good evening, folks. This post was inspired by a question from @Manofinterests asking about Boba U4 Thocks vs the silent ones (and their bumpers). I decided to compare the two stems close-up and share what I found.

Edit; more discussion including the Holy Boba below.

[ TL;DR: Tactile bump is the same, but I don’t recommend removing the bumpers. ]

Let’s start with some side-by-side visual comparisons at a few different angles:

The U4 bottoms-out on those soft bumper pads, while the U4T bottoms-out on the center post.

As you can see, the tactile bumps / legs are basically identical, while the center post on the Thock stem is lengthened to make it the bottom-out point - and of course there’s no silicone bumpers.

The bumpers are indeed quite easy to remove (and re-install, thankfully) - however, removing them does change how the stem interacts with the housing:

So - my conclusions are as such:

  • U4T’s are un-silenced U4’s, but with shorter travel (and of course THOCKNESS) thanks to the post.

  • U4’s without the bumpers aren’t the same as U4T’s without the long post; they technically work but not as intended, with the stem resting higher and having some weird-feeling pre-travel before otherwise normal function.

  • One more thing to note about silenced Outemu stems in general: while removing the bumpers is easy, the plastic rails that hold them aren’t meant to be bottomed-out on, and will likely wear out and collapse pretty quickly without the bumper there to support them.


Thanks for the review! I keep going back and forth on wanting these. They do sell out fast.

Any feeling on these vs holy boba?
Also so these have the holy boba problem where you hold down keys and it feels wobbly?

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Between the Thocks and Holy Bobas, I personally prefer Holy Bobas. Just like regular U4’s, U4T’s have a very long, round bump; and in comparison, the Halo’s is a bit shorter and snappier, which I like.

Unfortunately, both do suffer from the wobbly-at-bottom-out factor - pretty much every switch I’ve tried that bottoms out on the post is like that.

If someone can figure out how to totally mitigate that feeling while retaining the sound benefits… well. I’ll buy that person’s switches. Closest thing to that right now might be Caps, mostly because of their deeper sound and stable bottom-out.


How does sound differ between thocks and holy bobas?

Thanks. I am going to pass for now too close to what I have now. I have a few sample silent linear stems coming to change things up.

Great post and nice detail. I have some of the thock stems coming and I’m excited to try them out.

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So comparing the sound of these (U4 Thocks and Holy Bobas) ended up being more interesting than I thought. Which one sounds deeper depends on the case, but also how hard you hit the switches. Here’s a quick recording alternating between the two switches, starting with the U4T:

I have them in a small tester with rubber feet, held against an over-turned keyboard case.

Striking the keys “normally” makes the Holy Bobas sound deeper than the U4T’s - but hitting them a bit harder brings out a sharp element to the HB’s sound that the U4T’s don’t have; so depending on your case and how you type, it seems Holy Bobas have a pretty wide “vocal range” compared to the Thocks.

Stock, the Thocks have a bit of spring crunch, but I’m sure Gazzew intended the springs to be donut-dipped, or at least lubed in some way.

These are both loud switches, but it’s a little easier to type less-loudly on the Holy Bobas if the need to be gentle arises.


Thank you, that’s really interesting.

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Thank you, that’s what I call a good audio comparison.

I also still have Holy bobas but not yet installed because I can not decide for the lube 3203 or 3204.
Boba U4T I have also ordered, these are on the way. The housing of the U4T is I assume exactly the same as the U4? So I could make more Holy bobas with these if I don’t like them.

Interestingly, based on your sound test, I think the sound of the U4T is better (it’s bassier). I’m curious to see the direct comparison when the U4T arrive.


Yep - they both use the same Boba housing. :+1:

For Holy Bobas I might go for 3203; it should smooth-out the mild leaf-roughness without dampening its lovely crisp feel or sound too much - but of course this is a preference thing. I’d do one of each and put them in a tester to see which suits you personally.


Appreciate this comparison! The U4Ts definitely have a wood-like thock to them which is quite nice. Might stick with my Holy Bobas just for the snappier feel of the bump but glad to hear there are more tactile options coming up


Thank you so much for this! I did a de-dampened U4T stem. Very tactile, but after a while, the tip of the rails that held the dampeners can bend causing the stem to get stuck–so I don’t suggest this method as well.

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I wonder if the empty bumper rails on the bobas would be good excess lube holders lol


U4 squishies! :rofl:


Recently tried the U4T stem in different housings to compare to Holy Boba with all of the same spring weights (74g NK spring). Was hoping to find a good option for medium-round tactility as the Holy Boba may be a bit too sharp for me:

Boba top/bottom (standard U4T) - Longer/rounder tactility than the Holy Boba but definitely less sharp and a little lower pitched on bottom-out
Cherry Silent Red housing - Longest travel of any combo and feels like a proper switch. Pretty thocky and enjoyed the tactility decrease compared to the U4T and Holy Boba + slight pre-travel compared to others
Sky bottom/Boba top - Very similar to Boba U4T with a small decrease in tactile sharpness, but clackier than expected
Gateron KS-3 housing - Very short travel, abrupt bottom-out (loud as a result). Tactility similar to the Cherry housing but less thocky and more clacky (w/ and w/o films). Was excited for this one but the travel/sound are just not for me
Alpaca housing - About the same travel as the KS-3, perhaps even less. Too shallow for me. Reduces tactility quite a bit with really no benefit for sound/feel. Not sure why I tried this, but I wouldn’t ever use these.

I want to try a bunch of the Cherry linear housing version on a full board at some point to see if that range of tactility is more my speed. Happy to try more combos as needed; though I don’t have a ton of additional options to test. Overall, I really like the stem and think it accomplishes what it set out to do


very thanks

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I put some U4T stems in Boba housings and I like them ok, but I’m looking for other housings that they might work better in.

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I got some older Gazzew silent tactile stems, and they’re great. I’m gonna compare them side by side with some Boba U4s, but I think I like them better.


They’re definitely very different, but I think I might like them better, too. That U4 bump is too big and round for me, while these other ones are a bit more crisp.

There are elements of the U4’s that I think might be more polished - say, the tolerances with Boba housings and how they fit well with the leaves - but I prefer the actual bump profile of the older silent tactiles. I put together some switches using those and the leftovers from Holy Pandas (Halo housings, Panda springs) and they were quite nice.


Ooo nice idea. I might be buying more from Gazzew before they are all gone :smiley: