I recommend the Swytch package for Brompton as a very neat solution. I cannot speak for the other versions for other bikes, but I can certainly say that for Bromptons it fits very easily The overall weight added to the bike seems to be very minimal and it remains easy to carry, this was very important to me as I use it to commute and have to carry it to and from the train. The benefit of the electric power is better than expected, I had watched many videos and reviews before buying but not actually had an opportunity to test ride or try it in real life until riding it on my bike after installation. So for anyone else wondering before buying what it is like to ride, I can honestly say it is worth the wait for the incredible boost!