a quick search of this forum with the terms "Miller's Mule Cam Gears" will net you a LOT of information.
My opinion (and what I believe is probably a forum consensus) is that Miller's Mule products tend to be very well thought-out, and just as good in their manufacture. Very high quality pieces, which will work, every time, exactly as intended.
They are not the ONLY ones producing high quality products like Adjustable Cam Gears, but you will not be disappointed if you choose to buy from them.
I'm no Boy-Racer..... but if I can't take every on-ramp at TWICE the posted limit.... I'm a total failure!