The Brompton block accessory allows the powerpack to be mounted at the front luggage port on Bromptons.
There are several advantages to this. As the powerpack is lower down, its weight has a less noticeable impact on the steering. It also leaves space on the handlebars, so handlebar-mounted accessories, such as a bag, can still be fitted.
Some Bromptons also have particularly awkward handlebar setups, which may make a conventional handlebar fit a bit more tricky - most notably, for many 'M' type handlebar setups. For these instances, the Brompton block provides a clean and elegant solution.
Find out how it is installed here: https://swytchbike.zendesk.com/hc/en-gb/articles/360007666278-Installing-the-Brompton-Luggage-Block-Adapter