A type of mountain bike
. Both front
versions are available. Designed to stop the dreaded crud
fouling up your cables and spraying up into your face.
The latset version for your rear wheel has a new, more complicated fitting, which invlolves connecting fiddly stays to your mudguard eyes and the mudguard itself. The older, and in my opinion superior, design had a simple bracket which attached to the seatpost of your bicycle.