moderator007 gets all the credit and my thanks for pointing out the proper size and a good type for the ball. I got 10 to have in hand 
He also pointed out other trade secrets I will look into in due time
My sincere and deepest gratitude!
Your original ball looks like a 3/32 ball, can you take a precise measure to see.
I measured the original ball at 2mm and have used that size in several RRT-01’s and TCR-1’s.
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You got me wondering what happened here, so I went and measured the ball out of a brand new never opened TCR-1 I just modded.
It measures 2.38mm which is the 3/32 ball.
Its got me wondering if the ball had been replaced in the TCR-1 I original measured the ball in.
Either jetbeam used two different sizes (which I doubt) or someone had lost and replaced my TCR-1 ball with the wrong size.
I measured my wear replacement 3/32 ceramic balls at 2.38mm and the brand new original TCR-1 ball at 2.38mm so that would be the correct size ball.
I don’t know exactly what happened Pol77, I measured my TCR-1 ball at 2mm and ordered 50 of them with 10 3/32 balls as potential wear replacements.
2.38mm or 3/32 should be the correct size though. Puzzling why they would use a standard size ball and not metric.
It might be best to order a few of both sizes to make sure one will be a exact replacement.
Aha! The plot thickens! I will see how it goes with this ball and if it is smooth, I’m happy. If I do not like the feeling, I will try the larger size.
I have used the 2mm many times and wouldn’t have even known any difference if it wasn’t for your pic, then measuring a original one I know had never been replaced.
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The Si3N4 balls should be a permanent replacement that shouldn’t flat spot, they’re way harder than steel balls.
They also have a G5 geometric tolerance rating which makes it more true to a perfect sphere than the steel balls.
can someone verify the claim that there is thermal protection in the 2020 RRT-01 driver
output testing is showing 2020 driver is no brighter than the 2019 model, they reach about 550 lumens, according to tests done by HDS and myself.
there seems to be a difference in the components on the battery side of the drivers (bottom left 2019 vs bottom right 2020):
I can’t be sure without having one to test but what looks like a black 603 resistor just to the left of the numbers 200506 might be a thermistor.
I see they have moved components on the left side up a little to make room for two extra components.
Is the small part circled in green diode D3?.
thanks for your great observations and info
so, a thermistor does what? dims the light at a certain temperature?
I also see other changes, no idea what it all means 
btw, I received the 2020 driver from Jchang76 as a free upgrade, after I lent him a 2019 driver… I am very grateful to have the option to test the newest driver… Thank you!
I dont know, why do you ask?
D3 on the 2019 board is missing on the 2020 version.
Its a resistor that changes value with temperature.
You can read about it here.
It could be using a thermistor and a resistor (the two foghorne circled) to create a voltage divider like described in section “Hardware linearization solution”.
Its missing from the battery side of the board. It could be that it was relocated on the other side of the battery pcb, which we dont have a view of.
Its a two piece stacked pcb driver.
moderator007, can you say from the changes you see in the components what the purpose may be? Would the design dim the light to maintain a max temperature or will it work as a safeguard to shut it off if a temperature is reached?
If it is a thermistor it only gives the mcu a way to measure the temp. The code that compares the reading would determine where and when step down or shut down would happen. It was all up to the designer and coder as to the features.
So there is a possiblity the hardware is there but the code to take advantage of it is not.
I did turn on 2 TC-R1 lights, one with the 2019 and one with the 2020 driver and put them side by side on the table until they got fairly hot, but I did not push it because I have had a 2019 driver die on my a few days after I used the light for an actual emergency where I had to repair my girlfriends home lights that shorted. so the light was on top of a wardrobe on max until the battery almost died, while I was repairing the lights. It got quite hot but kept working and as the battery was depleted, output and temperature were lower and the light cooled off and kept working. A few days later, the light would suddenly not turn on. Replacing the driver fixed it. It looks like temperature killed the driver but not on the spot. In any case I am since reluctant to repeat the experiment and was excited to hear the 2020 driver may have some kind of thermal regulation / protection, but my short trial did not show it has. Maybe it needs to be tested for longer.
I would want an IR thermometer, to track temperature… or some fancy autologger like I see in some reviews
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trust but verify
regarding the 2020 RRT-01:
what is the parasitic drain when the dial is turned to minimum?
the 2012 has a drain of 55uA (selbuilt)
the 2019 has a drain of 27uA (djozz)
the 2020 has a drain of ~28uA (pol77)
I believe that those values are due to the different working of the drivers.
The one of the 2020 version is to be used along with a tailswitch closes the circuit energy, hence preventing the drain.
The 2012 and 2019 will probably act more like an e-switch that doesn’t completely shut down the energy circulation.
So, in my head, the 2020 driver version is probably projected differently than the ones of the previous versions, which are supposed to reduce the drain once the rotary ring acts as the switch itself.
Also in my head, it doesn’t seem to make much sense to use the 2020 version with the tailswitch ON and then only use the rotary ring.
It makes sense to dial a “level” through the rotary ring and then just turn the light ON/OFF, acting as a single mode light. Having a forward clicky switch is even better (for me), as it allows momentary on for the lowest modes without full clicking 
the question has come up repeatedly from people wanting to know if they can use the 2020 model on standby
edit
turns out, thanks to a test by pol77, that the standby drain on 2019 and 2020 RRT-01 is the same, I dont know if there is working thermal protection in the 2020 as claimed
Yup, looking at those values, it surely would be a downgrade as the originals would be more suitable for the lights than the “new” one.
I am not familiar with the new lights, I was only absorbing and reinforcing (althought without data) what you wrote before.
It really doesn’t make sense using the light that way nor modding other lights with a different driver, be it due the thermal sensor or not
Thanks for the explanation on this
and thank you for starting a wonderfully informative thread
My first reason to replace an RRT-01 driver, was because I destroyed one when disassembling the light incorrectly.
I have also intentionally upgraded from a 2012 driver to 2019 driver, in order to obtain the Strobe function
this is a good upgrade
the 2019 light also claims a 950 lumen output, whereas the 2012 driver claimed 600 lumens
that might lead some of us to hope that the 2019 driver will be brighter. Im not sure that is true, as I think the main difference is in the LED… but I dont have solid data
but here are the driver options I have seen Jetbeam use:
2011, no strobe, driver label says RRT-01
2012, no strobe, driver label says Eye10
2012, yes strobe, driver label says Eye10 (serial number on body is different format)
2019, yes strobe, driver label says Eye10
2020, yes strobe, driver label says Eye10
2020, yes strobe, unverified thermal protection, driver label says RRT-01
driver feature progression
original 20212 rrt-01, no strobe
2019 model, yes strobe, possible higher output
2020 model, yes strobe, plus claimed thermal protection
I just ordered a couple of spare 2019 RRT-01 drivers.