Our mini can fit a child slightly over 4' tall, as well as a man over 6'
Folding bikes place the seat tube behind the bottom bracket. This allows the seat tube to angle back. In doing so the virtual top tube length increases as the seatpost is lifted higher. This correlates arm length ( virtual top tube length ) to leg length ( pulling up the seatpost )
Our suspension based 20" wheel folding bikes will not fit small girls like the mini, but they will work for most riders 4'8" up to 6'4". Having one bike that fits an entire family is convenient.