For 26 inch wheel bikes like the DJ Fat Bike, DJ Mountain Bike and DJ City Bike, I would recommend to riders between 5'4" and 6' 4". As for the weight capacity, the manufacturer states the max weight is 275lb. However, I have 300 lb + customers riding the DJ bikes.
For the 20 inch wheel bikes like the DJ Folding Bike, I would recommend to riders between 5'2" and 6'2". The weight capacity is the same.
There is one more thing to mention. All DJ Bikes equip a shock absorbing seat post. If you replace it with a normal seat post, you can further lower the seat by 2 inches to touch the top of the battery.