With a plethora of stock and aftermarket choices, customization is a staple feature of owning a Ducati. This extends to the Monster. While I don't intend to market a selection of brands and items you can buy, there are many all over the internet for you to choose from.
The very first image is all you really need to know. The Seat lifts out of place one the key is placed and turn into the lock slot on the rear frame. My bike has had quite a bit of work done to it to eliminate the rear fender and extraneous metal.
Next >
Ducati is a registered trademark of Ducati Motor Holding S.p.A.
Various images taken from Official Ducati Manual