When fins aren’t needed (if you’re not on sidehills or icy, hard packed downhills), it’s best to stow them away so they don’t cause too much friction.  In snowy conditions the friction won’t be very noticeable but on hard pack it would be best to stow them away.  To provide the option, we have created a system for the Paris that allows the fins to be removed and either mounted inside the sled or stored in your pack. In the Snowclipper we took it one step further and designed fins that are retractable.