Gosh, this is good news. To this point I made dip pen holders by lathing a piece of material to hold the section and then reduced the point to hold the nib. Buying these makes it really easy. Are they made in the U.S.?
You can also use the kit nibs without the feeds to fit in the inserts. The above link is good for a few inserts, if you want to buy in bulk at a better price go to Styles and Bates in the UK. They will ship to the US.