the T115 has the smallest tips for micro soldering, they are tiny, T210 is the next size up and is more usefull to be honest with you. i find the t115 tips all but useless apart from the smallest components.

I have a T36b with a 115 handle and had to keep swapping for the 210 handle all the time, so i bit the bullet and bought a sugon T3602 dual handle setup, but with both handles active and no swapping and messing about.