They aren't exactly primitive but neither are regular nutters.
The toothed washer grabs the grass and keeps the arrow from snaking underneath and getting buried. It'll stand the arrow up purty good in taller grass and makes an awful tearing sound when it hits stuff.
I have yet to shoot a critter with one so I don't know how well it' would kill stuff but it seems like it would sure impart the wompin' on something.
Another cool thing is that with the larger nut , two toothed washers and the 1 1/4" drywall screw it brings the weight up closer to a field point. Haven't weighed em yet but they fly just ike my field points.
The nut is just a regular 5/16"( I think) nylon bushing nut, taper the tip of the arrow a little til it screws on tight. Then pilot a hole for the drywall screw, slip the washers onto the screw and insert it into the end of the arrow.The little washer keeps the larger one centered on the screw.
Theres reall very little tapering that needs to be done. Just enough to get the threads started .
I want to try them out with larger toothed washers but thats the largest kind I had on hand.
Hope you enjoy 'em.
Chris