These are screw inspired stones for the game Tak.

See my other entries for a 5x5 game board and case.
You need 21 flat stones and 1 capstone for a 5x5 game board for each player.

I've attached a file on how to play Tak taken from the Wikipedia article on Tak.
Tak has very simple rules like checkers, but the game can get very dynamic with multiple play options like chess.