The wheel width of the 2 frame wheels, rear fold under, is just not that far apart...
(As Is people complain about their heels hitting them, pedaling, as wide as they are)

the after market accessory mentioned above, was created, by a 3rd party vendor, to resolve that lack of width, & be retractable.

[I have an M3L, with their EZ wheels, it is adequate, it does fall over, occasionally , small bump is all it takes ]





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