Ingenious telescopic mudguard which hides under your saddle and can be pulled out to keep your behind dry when it rains.
For extra cachet it's made by Japanese NJS approved saddle maker Kashimax.
It clips to the sloping part at the back of the saddle rails. The distance between the rails here varies saddle to saddle and it's easier to fit to some than to others. There are two different clips included with slots 52mm and 58mm apart.