Mucky Nutz Fat Butt Fender It is fitted as close as possible to back face for optimum muck catching It prevents the top of your seat post from getting clogged up Discretion is its middle name; It's small but effective It's possibly the lightest fat bike mudguard available, at just 45g It's compatible with all standard double rail saddles, so long as they don't have any daft bits hanging off the rear