You may have noticed in previous photos that I didn't have a shift knob. It was also something I wanted to work on.
I have the STI piston shift knob and have been suffering with the worn plastic adapter pretty much since I've had it. (Got it used from a former friends' roommate in '06? '07?) It was silicone'd together this entire time and couldn't shift too harshly or it'd come loose.
Although I understand what the numbers for thread sizes mean, I'm not 100% sure how you're supposed to measure them, so I set out and got a new thread adapters.
They are: 16x1.25mm, 20x1.5mm, 18x1.5mm and the original plastic crap.
The 18x1.5mm fit best. I took advantage of the hex-head portion of it and clocked it straight on the shifter.