The standard monorail of the Concept 2 Model D indoor rower handles people with an inseam up to 36 inches. Users with a height of up to 6’8” normally fits the standard monorail.
With fully extended legs the seat rollers should not hit the end of the monorail. An extended version of the monorail is offered by Concept 2 and it adds 5 inches. On the Model D you can reach well in front of the footrests when in the catch position without hitting the PM5 performance monitor or the flywheel housing.