At a glance, the Retrakt is probably the most 'normal' pen in Karas Kustoms' line-up. It looks somewhat reminiscent of classic ballpoint designs, like the Parker Jotter, with the option of coloured lower barrels. But the coloured barrels are all annodised aluminium, not plastic. The clip isn't a flimsy bit of bent steel, it's thick and solid, and held in place with two bolts.
It's also a far more flexible pen than most - it can use a huge range of different refills. As standard, it uses many different 'euro format' refills (ones with solid tops), probably the most common shape for rollerball refills. With a supplied extender and alternative spring, it can use standard 'Parker-style' G2 ballpoint refills.
If you'd prefer a shorter pen, at the cost of not being able to use the long 'euro format' refills, try the EDK.