Mike , They're smaller in diameter .....example my 340's are probably the same size as a 3-49 A/C/C !

The insert system allows the insert to be placed inside the shaft. Then you can true up the front with a provided champfer stone an get good broadhead fit !

Whatever layering is used....coupled with the smaller diameter......supposedly makes them super tough! There are claims that you can shoot them into a brick wall without damaging the actual shaft !

Kinda hard to believe that !

The few I have shot ....seem to shoot good and spin true ! But I have only tested a few out of the dozen and I just replaced my disk in my WB to one of the new brown ones.......so I am in a test and tune mode right now !