I am using a Swytch AIR kit on my Brompton. The riding experience is great, but fitting the kit is more difficult than Swytch lead you to believe. The pedal sensor is the most tricky and makeshift part of the kit. Just this part took me 1½ hours to fit. They send you pedal crank components for different bikes and I first had to work out which ones to use. The paper and online manuals have contradictory information about where to install the sensor. I eventually realised I had to take a deep breath and cut its bracket off with a hacksaw (this advice at least comes with reassurance that it "won't invalidate the guarantee") and use two provided sticky pads instead. The cable ties provided are not long enough for this component and it took me a while to realise I could join two together 🙄. The instructions show two cable ties side by side but there isn't room and I made do with one. Its connector cable is near the rear folding bracket of the bike and I worry it's going to get snagged or crushed when folding or unfolding it. Then the battery bracket comes with numerous different spacers for different diameter handlebars and working out which ones to use while preventing them from falling out before fitting is tricky. I fixed it on the back of the handlebars which allows normal folding of the Brompton but leaves the bracket a bit vulnerable on the outside when folded. You can attach it to the front and use the provided longer 'Bro Peg'. The battery bracket is then on the inside but the fold is less compact. I got a bike shop to put a new inner tube and tyre on the wheel. The forks on my bike were only just wide enough to fit it and I had to discard some washers. Finally, finding the best routing for the various cables took some trial & error and again the instructions were ambiguous. The result, though, is brilliant. Two or three turns of the pedals starts the motor. It is on or off (no gradation) but very smooth, and stops instantly when you stop pedalling. I strongly recommend the optional extra £30 LED controller which allows me to set power levels 0-5 and the maximum speed at which the motor cuts out, once I worked out how to use it. I started with Power 3 and 26 kph (16mph) but the battery ran down quite quickly. I now find Power 1 and 21 kph (13mph) just as good for my mostly flat journeys (although it also goes up gentle hills well) and the battery lasts longer. The battery level displays on the controller and the battery itself give contradictory information about the remaining charge - the controller is more reliable as the motor stops working when the controller shows no charge but 2 out of 5 lights are still on on the battery. The controller acts as a speedometer (kph or mph) in use if you select the correct wheel diameter in the settings. With the power off, the bike runs exactly as before, although the front wheel doesn't seem to rotate as freely (they reassure you about this). You can also pedal harder to exceed your set maximum speed without motor assistance. The battery charges in a couple of hours maximum. It was well worth the hassle of installing the kit and riding my bike is a lot more fun!