The posterior is right up there when it comes to bits you want to keep dry. Yet here in London in particular there's a certain type of cyclist that doesn't want to burden their bike with a proper mudguard. Enter the Ass Saver. It's a tiny little bit of folding plastic that slots in underneath your saddle. When it's dry, it hides away underneath; when it's wet, it unfolds to provide a wedge-shaped bit of bum protection from spray arcing from the top of your back wheel.