The Sap Cap’s crown conceals a “unique impact material,” which makes it a powerful and discrete weapon in the hands of a master.

This standard baseball cap can be used as a blackjack or sap. Just use the bill as the handle and the cap as an impact weapon. The secret of the Sap Cap is the pocket of a unique impact material that is 110% the density of lead and will not rust. Velcro adjustment.

Good, one supposes, for self-defense in those places where the customary equipment is not legal. And it’s cheap, too: it’s $30. One reviewer, however, offers an explanation why:

It’s a standard 6 panel Velcro closure hat but the panels were uneven making the entire hat lopsided. What good is a self defense hat if you’d never wear it? … It does what it says, it just looks terrible and fits uncomfortably while doing it

Product Page [Dubk via Giz and Fashionably Geek]