It is a scientific fact that all a girl really needs for any given vacation fits easily into a tank-bag: toothbrush, bikini, a little black dress, heels, sunscreen, lip-gloss, mascara, and a tire pressure gauge. Girls who ride motorcycles know this. No bulky bags crammed with “essentials” like clean underwear and shampoo that you’re expected to schlep around for her. Chances are, we’ve got a cool tank bag that doubles as a stylish purse anyway.