Jenex rollerski brakes
 

If anyone is interested, I've been trying Jenex's new brake that
mounts on the Aero skis. (I use the skate 125's.) Looks really ugly,
but works very well, particularly with speed reducers. Definitely
opens up a whole lot more terrain!. Extra weight didn't seem
noticeable, and the ability to panic-brake is really cool.

Matt