The compact M1 with Downhill Control. On flat parkland you may never need it; on anything undulating it is the difference between walking beside your trolley and hanging on to it. DHC holds the trolley to your set speed on the way down instead of letting gravity decide.Otherwise it is the M1 as it should be: one simple fold, a wide LCD you can read in sunlight, nine speed settings, and a frame that stores small. The 18-hole lithium battery clips in and out with no cables.