You become a master at technology, you can quickly grasp the principles and applications of any Tinker Specialty you possess.
You also gain the Tinker equivalent of any powers you purchase, as well as the ability to imbue, channel, and create tinkertech items with your abilities, such as powerful mechas you can control with incredible precision that is specifically tailored to and can utilize your powers. (If you possess Glory Girl’s power you can create a mecha that has her force fields and aura, and if you have Eidolon’s power then you can make an automaton that can gain any 3 powers at a time, etc..)
Additionally, your Tinker Specialty can obtain permanent slots for your Tinker Powers at a reduced price. You only need to spend one-third of the normal SP cost for T1 Tinker Powers and half of the normal SP cost for T2 Tinker Powers.