Rivet Nuts? How big is too big?

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If you are doing a lot of 1/4 and 5/16 you will want the tool John pictured. I have done a few 1/4 inserts with my pliers but, if I had more then a couple to do, I would get that one to do them. I borrowed that same tool from work when I built the K-member for the van floor. Made it pretty easy.
I can install #8's and #10's all day long with my Marson pliers. In fact I have been using a set I got from Harbor Freight the last few days to install aluminum riv-nuts in some electrical panels I am building for the van. Work very well...
Mark