And these Kai's shave as good as the Feathers? It looks like they are industrial or box cutters. I mean I'm open to try anything that works and then settle in on what works best.I use the KAI Best .25 in my Core. I like it better than the Feather FAS. Works just fine. But: it is carbon, so you will have to see if it is for you.
Here is where I got them (ebay):
KAI / REPLACEMENT BLADE (50 SHEETS SET) / BEST0.25 / MADE IN JAPAN