I can't seem to get these to import into Hex Kit without some kind of misalignment. They look fine in the import dialogue and I'm able to adjust the tile so that the yellow line is on the line, but when using them in the editor, the tiles are too wide and there's either overlap or a gap, as if the tiles are too wide.
Edit: After banging my head against this for a while, the problem seems to be that some of the assets are not square. I assume these are not tiles at all, but rather are meant to be used with your other utilities for customizing tiles. (For context, Hex Kit's default tileset comes with empty borders as the base for a new map, so it didn't seem strange to me at all that empty borders would be a tile of their own.)