Want a REALLY simple knock off version? Drop a hunk of a drill bit inside the shaft of your arrow. Exact same principle.

Better yet, take 2 junk arrows, a standard foam target, and 2 drill bits. Glue one of the drill bits tight at the front end of one arrow behind the ferrule, this will give an equal mass arrow to the slip hammer test, but will simply give a RIGID, non-slip hammering arrow with a HEAVY FOC. The other drill bit, simply insert inside the nock end, letting it slide to the rear before your shot.

Shoot the block. Dollars to doughnuts, your fixed/glued drill bit arrow will out penetrate this BS slip hammer junk.