It not only collapses down to fit in a bag or a purse—it’s stylish, too.
We can debate all day whether or not, given proper infrastructure, bike helmets are necessary. Regardless, in America, the infrastructure isn’t there, which makes helmets something everyone should wear. But we don’t, for a variety of reasons: because they’re bulky to lug around all day, because bike sharing programs like CitiBike don’t offer them, or because we’re thoughtless assholes with a god complex.