Synthetic Ruby Sphere, Grade 25, 0.0059' Diameter (Pack of 50)

Incredibly smooth bearing ball. These should not be used anywhere they are subject to impact because with extreme hardness comes a brittle surface. In no impact applications they seem so spin forever.

I wanted a ruby ball because it looked cool in the picture - but its a little thing.

I bought this on an impulse. It is kind of cool and my daughter loved it.It is small, though, just keep that in mind, really small. That 0.22 is DIAMETER, not radius. Measure/draw out just under 1/4 inch so you know what you are getting.The color is not as rich as the picture and it really doesn't look like a ruby to me. I just take their word for it.Fun factor=4 starWhat you get=2 starAverage=3 starI probably wouldn't do it again.

I bought these to replace the worn-out original steel bearings on my vintage Microsoft USB Trackball Explorer (model X08 1.0 MS Trackball Explorer for PS2/USB, 46mm ball).. You wouldn't expect the plastic trackball to wear down steel bearings, but it's the dust from your hands that ends up wearing a flat spot on the bearings. The flat spots lead to sticky ball motion within a year or two of use.I just carefully pried out the old balls with a pin, then pressed the new ones into the sockets with my finger. Took all of 5 minutes. 2mm (0.0787") is exactly the right size. You could also use synthetic sapphire balls which are basically the same thing as ruby except they're clear. Ruby can shatter and won't carry anything like the kinds of loads that steel or zirconia can, but that's just not a factor when the load is just a 2 ounce plastic trackball.The trackball's action is now better than the new trackball ever was because ruby has no "grain," as opposed to steel which has a very fine grain structure like microscopic concrete that causes some drag on the ball. These ruby balls have even smoother action than the fancy zirconia ceramic bearings I've tried in the past.The big news is that, two years of heavy use later, there's no sign whatsoever of wear on the balls and the action is still better than new. I don't expect to ever replace these since the ruby is much harder than any dirt or dust particles (except for ruby or diamond dust).Update: After 3 years, the Trackball's action deteriorated and I found small flat spots! Still, 3 years is much better than the original steel balls. I just pried the balls out and put them back in, making sure the flat spots were face down. Works like new, again.Update: Someone asked if the harder ruby bearings scratch the plastic trackball. No. Trackball is still perfectly glossy looking after all these years. Anything that runs smoother will also cause less wear, and these rubies are glass-smooth. Also, I'd expect less wear caused by ruby balls than steel since the steel balls get worn by dust, and that worn area will be rough, gouged & jagged steel at the microscopic level. Also, Elcom introduced their new huge ball trackball which runs on... synthetic ruby bearings.

It looked pretty so I bought it. I may have a use for it someday.