uxcell R188ZZ Deep Groove Ball Bearings Z2 1/4 in x 1/2 in x 3/16 in 10pcs

AKA: The “You Didn’t Know You Needed These Until You Did” Bearings These R188ZZs are the sleeper MVPs of anything that spins. I grabbed them for a 3D printed mini turbine project, and they’ve since found their way into a fidget spinner rebuild, a sliding drawer mod, and even a DIY rotary encoder test rig. They're shielded, compact, and smooth as silk when installed properly. Z2 tolerance means you’re getting solid mid-grade precision—not quite aerospace, but plenty good for most hobby and light industrial builds. Pop these into a printed housing or bearing block, and they’ll quietly spin forever while you admire how much smoother everything feels.

Work as they should.

Perfect for my hermit crabs spinner.

These were slightly undersized on the outer diameter, but didn't cause any issues on my project due to not boring the holes until the bearings arrived. These bearings also have a lot of lateral movent, and will look like they are about to come apart with light side loading. They did however hold up to being assembled with a .001 press fit bore and shaft. The bearings are smooth, not rough or gritty, and have decent metal sheilds. They are decent little bearings, but I personally couldn't recommend these bearings for high speed, robotics, anything CNC, or 3D printing.

nice little bearings. I needed to replace some metric with 1/4" x 1/2" o.d. and these fit nicely. I did have to shim the outside of the bearing using some .0002" brass shim stock but that was only because the the bearings were metric before and I needed to use an axle that had 1/4-20 threads on it. I have some spares too.

Used this for a FRC climber. diameters are true to size. Decent bearing for the price. Obviously not a precision high speed bearing. I have bought many of these... over 100 for teams 3197 and 5586

Amazing

I bought these to replace the damaged bearing in my fidget spinner. They are okay. Just okay. They rotate smooth and are decently quiet, but they maintain no momentum. The moment you stop applying force, they'll stop rotating. The bearings I had before could rotate for well over five minutes with a single strong flick. This go two seconds at most, and I wish that was an exaggeration. I don't know if it's because they have a lot of grease/lubricant in them or what, but generally I'm disappointed with them. If you just need something that turns smoothly when pressure is applied, these will do great. They fit as expected and would be well priced for that purpose. But if you need it to keep spinning, then these ain't it.