I have no idea what a Hi-Tec-C is, why is it so awesome? 
If you've ever written with one, you know what we're talking about. 
Read more about Hi-Tec-C pens on JetPen's blurb

You kind of have to just try it. 

A little googling will also bring up a lot.
Here are a place to start.

What ink cartridge comes with the Pen Type-A?
The Pilot Hi-Tec-C Black .3mm width tip
What ink cartridges fit in Pen Type-A?
All Pilot Hi-Tec-C and G-Tec Cartridges fit in Pen Type-A. 

Can I get my pen with a different width cartridge? or a different color?
We ship the pen with a 0.3mm black ink cartridge.  Hi-Tec-C pen refills are available in black, blue, and red ink colors with tip sizes of 0.25, 0.3, 0.4, and 0.5 mm. If you want a different refill you can find Hi-Tec-C pen refills and other cool stuff at