I have the one for aluminum arrows and have fletched all three with it. The 3/8 dowels are about max for it and if you crest with contact paper it is a real tight fit. The really skinny carbons are a trick to fletch with it though.
If you haven't purchased one I would buy somethng else. It is quick at first but you have control issues feathers. They want to slide if they are not ground perfect. Also, glue build up is an issue on the plastic arms. I like to make sure I have enough glue but any glue that comes out the sides hardens on the opennings for the fletching. You have to stop every 4 or 5 arrows and scrape then lightly sand the opening so you can get eh feathers in. It is a bit of a pain. I think with a single feather fletcher and fletching tape you could finnish arrow faster and have a better quality arrow. I almost forgot about another issue. When the glue dries to both the feather and an arm you sometimes pull the feather off opening the EZ.
It does work as advertised and I've had mine for years, but I think there are better tools for the job.